This PDF file contains the front matter associated with SPIE Proceedings Volume 11228 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

A novel design of tunable-lens-integrated miniature handheld OCT probe, with high-speed angiography function, is proposed for use in clinical settings for young children and infants, providing rapid, non-invasive retinal imaging of vitreoretinal features as well as retinal microvascular information. Compared to conventional OCT systems, the proposed system and probe would promise a suitable tool for diagnosis and screening of retinopathy of prematurity.

In this study, we demonstrate a novel self-tracking method to suppress eye motions on wide-field optical coherence tomography angiography (OCTA) with a high scanning efficiency. GPU-based real-time OCTA image acquisition and processing software was developed to calculate the eye motion artifacts. An instantaneous motion index was introduced to evaluate the strength of motion artifact on en face OCTA images. Areas with suprathreshold motion and eye blinking artifacts can be rescanned in real-time.

We demonstrate the first 1050nm MEMS-eVCSEL co-packaged with a wideband amplifier to achieve over 70nm wavelength tuning at over 30mW of output power and SMSR greater than 40dB. Ophthalmic Optical Coherence Tomography Angiography (OCTA) images acquired at 800kHz A-scan rates showcase the telecom grade 14pin butterfly co-package as a path to low cost swept source OCT engines. Device design employs a strain-compensated InGaAs/GaAsP gain region disposed on a wideband fully oxidized GaAs/AlxOy back mirror capable of tuning ranges beyond 100nm. It has been suggested the wideband fully oxidized GaAs/AlxOy back mirror may pose risk to device lifetime reliability. However, over 9000hrs of lifetime testing validates reliability and projects device lifetimes exceed 20,000hrs under continuous use.

We present here an all-fiber Few-Mode OCT system making use of a modally specific photonic lantern to simultaneously de-multiplex light exciting the first two propagation modes of a few-mode fiber. Each mode collects a distinct projection of the scattering phase function from light backscattered by the sample. This implementation is mechanically more robust, has an optimal interferometric contrast and is compatible with commercially available OCT systems. We present a proof-of-concept through the imaging of micro-beads generating varying contrast depending on their relative size. Such a system offers an additional means of intrinsic contrast for OCT.

In this communication, we evaluate the suitability of Master-Slave (MS) optical coherence tomography (OCT) for processing of interferograms generated by an interferometer driven by an akinetic, electrically-tunable swept source from Insight with an ultra-large instantaneous coherence length. The akinetic source is programmed to sweep linearly, but within the sweep, at predictable times, the laser tuning introduces invalid regions in the interferogram, which are normally removed post-acquisition using a pre-calibration file. This makes sure that any optical frequency component is used once only and enables correct operation of a Fourier transform (FT). A FT applied to an unprocessed emitted spectrum leads to wide and numerous peaks in the A-scan. MS processing was introduced to avoid the necessary corrections demanded by conventional FT signal processing or its derivatives. The MS procedure consists of comparing photo-detected signals at the output of two interferometers, a Slave and a Master interferometer. The MS method was advanced along two avenues, either by using (i) electricallygenerated master signals (making use of the same interferometer twice) or (ii) optically-generated master signal via a recently introduced MS down-conversion procedure. We apply both avenues to the Insight source. Approach (i) tests the MS principle as an alternative to the Insight file correction while (ii) demonstrates near coherencelimited operation at a large axial range (>80 mm) for which a too-high sampling rate digitizer would have been needed. In this communication, we evaluate for the first time the suitability of the MS procedure to OCT measurements performed with the akinetic swept source commercialized by Insight. Two modalities are evaluated to implement the MS processing, based on: (i) digital generation of the master signals using the OCT interferometer and (ii) down conversion using a second interferometer driven by the swept source.

Optical coherence tomography (OCT) has revolutionized diagnostics in ophthalmology. However, OCT traditionally requires an operator and patient cooperation to align a scanner with the subject’s eye and image a specific location of the retina. We have developed a robot-mounted OCT scanner that automatically aligns with the subjects’ eye by compensating motion and gaze. In addition to using face and pupil tracking feedback to align the scanner, the system uses gaze feedback to track a retinal region of interest, such as the fovea. We demonstrate our system by tracking the fovea of human eyes subject to physiological motion and gaze change.

Non-invasive functional retinal imaging in humans is of tremendous interest. By using phase-sensitive full-field swept-source OCT (FF-SS-OCT) we demonstrated simultaneous quantitative imaging of the optical activation in the photoreceptor and ganglion/inner plexiform layer. Since the signals from the ganglion cells layer are ten-fold smaller than those from the photoreceptor cells a new algorithms for suppression of motion artifacts and pulsatile blood flow in the retinal vessels is important. With improved data evaluation we simultaneously measured the activation of photoreceptors and ganglion/inner plexiform with high quality and were able to analyze the spatial and temporal response of cells in the ganglion/inner plexiform over more than 10 seconds.

We investigated clinical imaging of the human retina with visible-light optical coherence tomography (vis-OCT) with a 1 µm axial resolution. Imaging was performed with rectangular modulation of the scanning beam that reduced image speckle noise and preserved fine anatomical features. B-scans acquired with scan modulation revealed new anatomical features and demonstrated increased contrast to noise ratio (CNR) over regularly acquired B-scans.

Microscope-integrated optical coherence tomography (MIOCT) systems allow for 4D visualization of thin, semi-transparent structures during ophthalmic microsurgery. While these visualizations have greatly increased the information available to surgeons, new surgical techniques, such as subretinal injections of gene therapies, would benefit from quantitative measurements of structures imaged using OCT. Calibration of true scan dimensions in OCT is complicated by inter-patient ocular variability as well as poor control of scanner-patient alignment. We introduce novel measurement techniques for calibration and de-warping of OCT imagery which allows for accurate measurement of intraocular structures including subretinal microinjection bleb volumes in the ocular posterior segment.

Current-generation optical coherence tomographic angiography (OCTA) systems are slit-lamp based, which limits imaging to patients who are able to sit upright and fixate. Prototype handheld OCTA has demonstrated imaging of supine patients, but these systems are susceptible to bulk-motion artifacts that degrade OCTA resolution and contrast. Here, we demonstrate bulk-motion correction and multi-volumetric mosaicking of OCTA volumes acquired using our handheld spectrally encoded coherence tomography and reflectometry (SECTR) system. In addition, we leverage variable-velocity scanning to reduce OCTA acquisition times. We believe SECTR overcomes the limitations of current-generation handheld OCT/OCTA and will enable functional imaging in bedridden patients and infants.

A line-field, spectral-domain optical coherence tomography (LF-SD-OCT) system was build for in-vivo, non-contact, cellular resolution imaging of biological tissue at 2.5 kHz frame rate. Test images acquired from healthy human subjects show that the LF-SD-OCT is able to image the cellular structure of semitransparent tissue such as the human cornea, as well as highly scattering tissue such as skin. This system may serve as a valuable diagnostic tool to ophthalmologists and dermatologists for diagnosis and monitoring the treatment of various corneal and skin diseases.

High speed ophthalmic Optical Coherence Tomography systems are of interest because they allow rapid artifact free widefield retinal imaging. Space Division Multiplexing Optical Coherence Tomography is a high-speed imaging technology which takes advantage of the long coherence length of MEMs VCSEL sources to multiplex multiple images along a single imaging depth. We demonstrate widefield retinal OCT and OCT angiography imaging, acquired at effective Ascan rates of 800,000 Ascans/sec with imaging ranges of up to 11 x 7mm on the retina. A clinical study was conducted to compare ophthalmic SDM-OCT with commercial OCT and OCTa systems.

Using phase-sensitive full-field swept-source optical coherence tomography we already showed that morphological changes in the photoreceptor outer segments are detectable. Those signals manifest themselves in an elongation of the optical path length. Using improved post.processing we report on progress in detecting signals in the neuronal layers of the human retina. The spatially resolved signals show a characteristic time course and by combining these with simultaneous measurements of the photoreceptors we were able to generate a wiring map of the neuronal retina.

Optical coherence tomography (OCT) is a label-free, high resolution, and minimally invasive imaging technique that can produce depth-resolved cross-sectional and 3D images. We sought to examine non-vascular depth-dependent optical changes directly related to neural activity in the brain using OCT. Results of this study show a significant temporal correlation between non-vascular decrease in attenuation in ex vivo and in vivo seizure models and increased electrical activity during seizure. This study allows for a more thorough and biologically relevant analysis of the optical signature of seizure activity ex vivo and in vivo using OCT.

Central nervous system diseases start at the microscopic level; thus, in vivo deep brain imaging with cellular resolution is needed. Using the 1700 nm optical window, which has lowest ballistic attenuation for brain imaging, an optical coherence microscopy system was designed for in vivo imaging of mouse brain cellular architecture. Taking advantage of relatively low scattering at 1700 nm, neuronal cell bodies in the mouse brain were visualized through a thinned skull preparation, which minimizes inflammation and preserves intracranial pressure. Cellular architecture was co-registered with simultaneous angiographic imaging, showing the distribution of neuronal cell bodies relative to supplying capillaries.

Prenatal substance abuse is one of the main causes of birth defects. Depending upon the substance being abused and the period of gestation during which the abuse happens, the severity of the defect is determined. Although prenatal substance abuse during the first trimester is common, the prevalence of unplanned pregnancies in the United States have led to women continuing their substance abuse well into the second trimester. The second trimester is the peak period for fetal neurogenesis and angiogenesis. Hence, any exposure to teratogens during this period is known to hinder brain development. Several studies have documented changes in morphology and behavior due to exposure to teratogens during this period. However, not a lot is known about the changes in vasculature in the developing brain. In this study, we used angiographic optical coherence tomography, a functional extension of optical coherence tomography, to image acute vasculature changes in the fetal brain caused due to prenatal exposure to ethanol, nicotine, and synthetic cannabinoids (SCB). Results showed a significant decrease in vasculature in all three cases compared to their respective sham groups.

In this work we demonstrate the ability of in vivo optical coherence tomography (OCT) images to resolve all relevant structures of human peripheral nerves. Measurements have been acquired in more than 30 peripheral nerve surgeries using a commercial OCT system (Thorlabs Ganymede) with a hand probe, which can be directly placed on the nerve, covered by a sterile foil. The resulting 3D OCT images were processed using texture analysis to highlight structural tissue features of the nerve. A comparison of OCT images and corresponding histopathology slices was performed in order to confirm the visualization of the nerve’s structures by OCT.

Adaptive optics (AO) systems for retinal imaging have a small field of view (FoV) of 1°-2°. To increase the FoV we developed a multi-conjugated AO-system. By choosing different scanning patterns, aberrations introduced by the eye at different locations within the FoV can be measured by a Shack Hartmann wavefront sensor. A second deformable mirror that is conjugated to a plane anterior to the retina corrects for varying aberrations across the field. Retinal imaging using spectral-domain optical coherence tomography is performed with 4º x 4º FoV and imaging data including the visualization of the cone mosaic is presented.

In OCTA, resolution of retinal capillaries is limited by physical numerical aperture of human eye and the subject’s ocular aberrations. Adaptive optics OCTA has been demonstrated in instruments with large numerical aperture, originally designed for the visualization of retinal cells. In this work, we propose a high-speed, spectral domain sensorless adaptive optics OCTA instrument with a 3-mm beam to image retinal capillaries of all three retinal plexuses simultaneously, with high axial and lateral resolution. A novel and fast hill climbing algorithm was applied on the amplitude of six low-order Zernike modes to minimize ocular aberrations based on maximizing en face merit functions of the layer of interest computed in real time.

Optical coherence microscopy (OCM) is an efficient tool to acquire cellular-resolution morphological images. In our previous study, we presented a Mirau-type OCM which provides both in vivo cross-sectional (B-scan) and en face imaging with a broadband extended source. However, two issues were encountered in B-scan mode. One is the illumination efficiency is low because the illumination area is much larger than the area of interest. The other is the image quality is degraded by linear artifacts. In this report, we use a symmetrical illumination design to improve the illumination efficiency and image quality of B-scan at the same time.

Over the past decades, several techniques have been developed to measure cerebral hemodynamic parameters such as red blood cell velocity, flux and hematocrit using optical coherence tomography (OCT). Despite these advancements, two photon microscopy (TPM) remains the gold standard for functional cerebral hemodynamic imaging, though localized line-scan or bolus tracking. Here we developed an optical platform enabling concurrent imaging with OCT and TPM and perform co-localized and simultaneous velocimetric measurements with both modalities, with the aim of validating OCT velocimetric methods.

An image processing method was developed for automatically generating three-dimensional models of human uterine collagen fiber networks from spectral-domain optical coherence tomography (SD-OCT) images. A novel image processing scheme was used to segment the tissue from the image volume and divide it into “processing regions” that adapt to the tissue topology. Quantitative fiber analysis was performed on b-scan and en-face image patches, enabled by a custom b-scan preprocessing pipeline. Three-dimensional fiber architecture was analyzed in over 100 mosaic volumes from five different patients (2 pregnant, 3 non-pregnant), revealing a highly complex and patient-specific network of fibrous collagen and myocyte bundles.

Polarization-sensitive optical coherence tomography (PS-OCT) has been used to extract polarization properties of four different diseased lungs ex vivo, including fibrotic sarcoidosis (FS), chronic obstructive pulmonary disease (COPD), fibrotic extrinsic allergic alveolitis (fibrotic EAA) and cystic fibrosis (CF). An increase in alveoli size has been observed in COPD lungs. Furthermore, an increase in birefringence signal was observed for FS and fibrotic EAA. In CF, a few areas with thick patches of birefringence occurred. The results show potential of in vivo assessment of lung fibrosis. Histology slides of all lungs were acquired, and will be used to further interpret the results.

This paper report the development of non-invasive multi-functional imaging system for dental applications. This system is capable of detecting: 1) autofluorescence of the enamel, 2) red porphyrin of plaque, 3) the 3D-tomography of the hard/soft tissues and 4) functional angiography of said 3D-tomography data. The imaging technique incorporates molecular imaging (via light-induced autofluorescence, or LAF), 3D-high-resolution structure (via optical coherence tomography, or OCT) and angiography (via functional OCT, or OCTA) into one single imaging probe and platform. This development is crucial for our future research that would look into possible links between our OCTA findings and other clinical indicator such as red-porphyrin of plaque, autofluorescence of enamel.

A novel stable fiber-based multi-functional imaging system capable of simultaneously acquiring the birefringent and polarization artifact-free microvascular information within scanned tissue volume is demonstrated. A novel system design that can compensate for the changes in polarization state generated by the optics fibers is introduced to stabilize the imaging system. The proposed system is employed to visualize the birefringent components and the vasculature networks of the human skin in vivo.

Lichen Sclerosus is a chronic recurrent inflammatory dermatosis of unknown etiology, which affects both the skin and also the mucous membrane and is usually localized at the genital area. OCT angiography is a promising tool for microcirculation mapping in 3D with ~micrometer resolution. During the study, we developed and implemented a robust real time OCT angiography realization for routine clinical practice. This allows clinicians to combine structural OCT imaging with angiograms during routine clinical practice. Normal vulvar mucosa and dystrophic vulvar mucosa were analyzed by multimodal OCT. In the structural OCT scans of connective tissue, lymphatic vessels were visualized as contrast, low-signal regions. The angiographic images of the normal mucosa show dense, uniform network, mostly consisting of relatively thin vessels. Lymphatic vessel network presented by rare, very thick vessels. Further realization of OCT lymphangiography in real-time in parallel with OCT blood-vessel angiography can improve diagnostic capabilities of the multifunctional OCT in real clinical practice.

Line-field confocal optical coherence tomography (LC-OCT) is an imaging method based on dynamically-focused line-field time-domain OCT to generate vertical section images of biological tissues with cellular spatial resolution. We demonstrate here an improvement in the LC-OCT technology that makes it possible to also generate horizontal (en face) section images, as in conventional optical coherence microscopy (OCM) or reflectance confocal microscopy (RCM). This improvement is based on the implementation of a lateral scanning device using a mirror galvanometer to scan the laser beam laterally at a given depth. The reference mirror of the interferometer is mounted on a piezoelectric transducer to generate a sinusoidal phase modulation during lateral scanning in order to extract the tomographic signal. The LC-OCT device is capable of generating either a horizontal section image at an adjustable depth in the sample, or a vertical section image at an adjustable lateral position in the sample. For both operating modes, images are acquired in real-time (8 frames per second), with real-time control of the depth/lateral position. The user can switch between the two operating modes by clicking on a button. Using a supercontinuum laser as a light source and 0.5 NA microscope objectives, the image resolution is 0.9 × 0.9 × 1.1 μm³ (x × y × z), with fields of view of 1.2 × 0.5 mm² (x × y, horizontal) and 1.2 × 0.4 mm² (x × z, vertical). In vivo cellular-level imaging of human skin is demonstrated for both modes of operation.

Spectral resolution is a crucial parameter in spectral / Fourier domain Optical Coherence Tomography (OCT). The sensitivity roll-off is determined by the spectral resolution, while depth-dependent axial resolution changes are caused by spectral resolution variations with wavelength. Currently, spectral resolution assessment is performed using either a narrow linewidth light source or broadband interferometry. Although commonly used, these methods require either additional components or time-consuming procedures. Here, we present a simple method to directly measure the spectral resolution at all wavelengths based on excess noise correlations. We apply this method to a visible light OCT system and validate it against interferometry.

We present here advances on the Master Slave (MS) concept, applicable to spectral/Fourier/frequency-domain optical coherence tomography (OCT) technology. Instead of obtaining an A-scan from the sample investigated via a Fourier Transform (FT) or equivalent, the amplitude of the A-scan for each resolvable point along the depth is obtained along a separate output. A multiplier produces the product of the photo-detected signal from the OCT system with that generated by an Electrical or an Optical Master. This allows acquisition at a frequency comparable to that of the sweeping, much inferior to the frequency bandwidth of the channeled spectrum. 3 advantages of the down-conversion method are demonstrated here: (a) real time delivery of an en-face image; (b) axial optical path difference (OPD) range at the level of the source’s dynamic coherence length and (c): tolerance to fluctuations in the sweep of the swept source. The most important advantage of the down-conversion method is that it reduces the signal bandwidth considerably, to the level of the sweeping rate. This facilitates real-time operation. Conventional A-scan production can only be performed real-time if the FT processing is carried out in a time comparable to or less than the sweep time, which depending on the number of sampled points and dynamic range determines a limit of ∼ MHz sweep rate. Before even calculating a FT, acquisition may also be limited by the sampling rate of the digitiser. In conventional SS-OCT, the number of depth points can exceed 1,000, which for a sweeping time of 1 μs would determine signals in the GHz range. Using long coherence length swept sources, this number of depths could be even larger, hence the conventional FT-based method faces a bottleneck due to the time needed to calculate the FT, combined with the need to acquire data at many GS/s.

We present a detection scheme which is widely used in quantum optics to study spectral correlations of photons. It uses a fibre spool to induce wavelength-dependent time delay and a fast single-photon detector for measuring these time delays and consequently, retrieving the light’s spectrum. This technique enables OCT imaging at very low-intensity levels and with increased sensitivity.

Models of OCT imaging systems which are rigorously based on Maxwells Equations offer significant benefits over approximate models. However, these full-wave propagation models require greater computational resources, particulary when dealing with large samples. In an effort to reduce this computational burden, we present a means of synthesizing scanning-mode OCT image formation using only a single simulation with plane-wave illumination incident on a 3D sample. An angular spectrum approach is used to synthesizes focussed illumination, and we investigate how the optical memory effect may permit this approach even in highly scattering samples. Demonstrations show that the required simulation time is reduced by an order of magnitude when synthesizing OCT B-scans compared with previous methods.

In Fourier domain OCT, the depth profile is mirrored about the zero delay, limiting the imaging depth to half of the entire ranging space. We present a novel configuration for OCT to robustly remove the complex conjugate artifact. Our method utilizes the intrinsic delay of circularly polarized light in two polarization channels, using only passive broadband polarization optics and conventional polarization diversity detection unit. Our method is immune to sample motion and adds no restrictions to source bandwidth, imaging speed or computational load. 45 dB suppression of the mirror artifact is demonstrated by an SSOCT with some in-vivo images.

A virtual multi-directional optical coherence tomography method to visualize directional microstructures of the tissue is demonstrated. The directional measurement is achieved by numerical aperture masks applied after the data acquisition. So multi-directional images are created only a single measurement with no hardware extension. By applying several types of aperture masks, we created not only multi-directional images but also multi-structural-frequency images. These images showed the difference appearance which come from the microstructural directionality of chicken breast muscle sample.

Side lobe artifacts on point spread functions can be traced back to (1) fringe visibility variation across the spectrum, (2) errors in sampling instances, and (3) window functions. We demonstrate signal processing methods for correcting for all three of these issues. These methods require a system calibration step. If the systems slowly age, the recalibration step could be performed in the field with a fixtured target.

We present a filtering procedure based on singular value decomposition to remove artifacts arising from sample motion during dynamic full field OCT acquisitions. The presented method succeeded in removing artifacts created by environmental noise from data acquired in a clinical setting, including in vivo data. Moreover, we report on a new method based on using the cumulative sum to compute dynamic images from raw signals, leading to a higher signal to noise ratio, and thus enabling dynamic imaging deeper in tissues.

To achieve 3D high-cellular resolution, a great effort, in the past years, was made to develop Adaptive Optics (AO)-OCT systems. However, such systems require quite complex, expensive and cumbersome hardware, making clinical transfer challenging. Recently, we demonstrated that the use of spatially incoherent illumination in Time-Domain Full-Field (FF)-OCT offers a valuable advantage: the lateral resolution is almost insensitive to ocular aberrations that only affect the FF-OCT signal level. We took advantage of this property to image in-vivo photoreceptor mosaic without using an AO technique. Nevertheless, the FF-OCT technique was still facing some challenges in providing consistent and reproducible images, mainly due to axial eye motion and reduced signal level. Here, we present the Adaptive Glasses-assisted FF-OCT, where an adaptive lens is placed just in front of the eye, like spectacles, enabling correction of the first 10 Zernike polynomials, increasing the FF-OCT signal level.

Spatiotemporal optical coherence (STOC) imaging is a novel technique for suppressing coherent cross-talk noise in full-field swept-source OCT (FF-SS-OCT). In STOC, we use time-varying phase masks to modulate light incident on the sample. The modulated signals are averaged incoherently or coherently to yield cross-talk-free 3D images of the sample. We show that coherent averaging is only possible under specific hardware configuration. We explain this theoretically and confirm experimentally by imaging USAF chart covered by diffusers and the rat skin ex vivo. Finally, we present human forearm skin imaging in vivo. In all cases, STOC imaging reveals otherwise invisible sample features.

The sensory epithelium in the cochlea of the inner ear transduces sound energy into electrical signals, which are essential for a neurotransmitter release. Nevertheless, the in vivo behavior and correlation of the dynamics among each layer remains unclear. To assess the wide-range motion within a living organism, we develop multifrequency-swept optical coherence microscopic vibrometry (MS-OCMV). This method employed the wide-filed heterodyne interferometric vibration measurement technique, which can capture the full-field vibration amplitude and phase distributions with optical coherence microscopy (OCM). In this system, we newly introduced the broadband multifrequency supercontinuum (SC) as a light source. Manipulating the frequency interval of the multifrequency SC can determine the depth of the region of interest where the two-dimensional biological vibration distributed as well as to conduct 3D tomographic volumetric imaging. In this manuscript, we demonstrate the accuracy of two-dimensional surface vibration measurement and the underlying performance of 3D tomographic imaging. We report the measurement results of vibrational motions induced by sound stimuli on the sensory epithelium of a living guinea pig using MS-OCMV.

Dynamic Full-Field Optical Coherence Tomography (D-FFOCT) is a high transverse resolution version of OCT that records signal at the output of the interferometer as a movie over a few seconds. Analyzing the temporal variation of the signals reveals intracellular contrast which gives D-FFOCT the capability of identifying dynamic metabolic changes. We use D-FFOCT to identify oxygen induced changes in cellular metabolism at ambient (22%) oxygenation and at hypoxia (1%). Signal strength, calculated as an integral of the raw FFT spectrum, is significantly higher for 1% samples compared to 22% indicating that D-FFOCT is sensitive to changes in cell metabolism.

We utilized a visible light optical coherence microscopy imaging (OCM) system to investigate the intra-tumor heterogeneity of glioblastoma samples. Using a broad visible spectrum an axial resolution of 0.8 μm was achieved. Objective lenses with short focal lengths were integrated to achieve high transverse resolution. Large field of view images were acquired using an automatic moving x-y-stage. Attenuation maps were calculated from OCM data and cell-density evaluations were performed from corresponding histological sections. Cell density and attenuation data were evaluated. Our analysis revealed intra-tumor heterogeneity by varying cell densities and attenuation coefficients throughout the tumorous areas.

Here, we established NpHR Drosophila model, and demonstrated a heartbeat recovery process after red-light excitation induced cardiac arrest. The maximum heart rate (maxHR) and heart rate recovery time increased with prolonged cardiac arrest. ReaChR fly model was also developed to study the relationship of maximum pace-able heart rate (maxPR) with aging. Older flies showed decreased maxPR. An optical coherence microscopy (OCM) system was used to monitor the heart rate in vivo and in real time. The maxHR, recovery time, and maxPR could become promising indicators of cardiac health for various cardiac studies via Drosophila models in future.

We present updates upon our novel machine-learning methods for the acquisition, processing, and classification of Optical Coherence Tomography Angiography (OCT-A) images. Transitioning from traditional registration methods to machine-learning based methods provided significant reductions in computation time for serial image acquisition and averaging. Through a vessel segmentation network, clinically useful parameters were extracted and then fed to our classification network which was able to classify different diabetic retinopathy severities. The DNN pipeline was also implemented on data acquired with Sensorless Adaptive Optics OCT-A. This work has potential to subsequently reduce clinical overhead and help expedite treatments, resulting in improved patient prognoses.

Endoscopic Optical Coherence Tomography (EOCT) systems can perform in vivo, real-time, high-resolution imaging of the human esophagus and, thus, play an important role in the earlier diagnosis and better prognosis of esophageal diseases such as Barrett’s, dysplasia and adenocarcinoma. However, the high image throughput and massive data volumes make manual evaluation of the generated information extremely difficult. Unfortunately, the algorithms, developed thus far, have not been able to provide effective computer-aided diagnosis. In this study, we compare different machine learning methods for tissue segmentation and classification of esophageal tissue in in vivo OCT images. An automated algorithm was developed, capable of discriminating normal tissue from Barrett’s Esophagus (BE) and dysplasia. The classification was based on various features of the epithelium, extracted from EOCT images, such as intensity-based statistics, the group velocity dispersion (GVD), estimated from the image speckle, and the scatterer size, calculated using the bandwidth of the correlation of the derivative (COD) method. The comparison and evaluation of various machine learning techniques has shown that a neural network based approach provided the best performance, classifying Barret’s esophagus and dysplasia, for individual A-Scans, with an accuracy of 89%.

Segmentation of the retinal layers in OCT images is the critical step in analyzing OCT volumetric data for diagnosis and monitoring of retinal disease progression. Real-time retinal layer segmentation has become increasingly desirable with the increasing OCT acquisition speed. In this work we explored methods to accelerate image processing method to segment retinal layers in OCT B-scan images including graph cut and deep learning. We demonstrated ~30-ms and ~3-ms segmentation of 7 retina layers per OCT B-scan with graph cut and deep learning respectively. The accelerated OCT B-scan segmentation was then integrated with our GPU OCT image acquisition software.

We developed a custom convolutional neural network combined with long short-term memory , named FlyNet 2.0, to achieve accurate drosophila heart segmentation in the cross-sectional videos of drosophila heart acquired by optical coherence microscopy system. Our first version of FlyNet uses regular CNNs to only extract 2D spatial information from individual frames of drosophila heart OCM videos. LSTM utilizes both spatial and time information to further improve the drosophila heart segmentation performance. 500 thousands fly heart OCM images were employed to train and test with FlyNet 2.0. Drosophila heart OCM videos through multiple heartbeat cycles and different heartbeat dynamic recovery situations were tested with an intersection over union accuracy at 92%. With increased segmentation accuracy, dynamical cardiac parameters, like heart area, end diastolic diameter, and end systolic diameter, can be quantified more accurately for the study of drosophila cardiac disease.

The ability to detect multiple contrast agents simultaneously would greatly enhance Optical Coherence Tomography (OCT) images, providing nuanced biological context to physiological structures. However, previous OCT contrast agent work has been limited to scenarios where only a single contrast agent could be robustly detected within each voxel. We present a novel spectroscopic technique for de-mixing the spectral signal from multiple OCT contrast agents within a single voxel. We validate our technique in vitro and also demonstrate in vivo imaging of three spectrally distinct gold nanobipyramids, trafficking within the lymphatic system of a live mouse. This approach opens the door to a much broader range of pre-clinical and clinical OCT applications where multiplexed labeling is desirable.

Contrast for imaging the retinal microvasculature and the retinal pigment epithelium (RPE) is essential for pre-clinical studies of vision-robbing diseases. By integrating polarization diversity detection (PDD) with OCT angiography (OCTA), we have developed a novel quantitative multi-contrast OCT for imaging pigment in the RPE as well as flow in the retinal capillaries. An adaptive filter was developed for degree of polarization uniformity (DOPU) processing to provide improved measurements of melanin region thickness in tilted retina. The retinas of three mouse strains were imaged in vivo, with results demonstrating potential for simultaneous mapping of vasculature and melanin distribution in the RPE.

Developing suitable contrast agents is essential for multiplexed optical coherence tomography (OCT), which allows simultaneous imaging of different biomarkers, cells and flows in living subjects. However, few OCT contrast agents have shown multiplexing capability, especially in the second near infrared (NIR-II) window. Here we demonstrate that using gold nanobipyramds as OCT contrast agents, two separate lymph flows can be visualized simultaneously in a live mouse in the NIR-II window. We concurrently traced lymph flows draining from a melanoma tumor and peritumoral tissue upstream of the melanoma, showing these flows exhibit distinct drainage patterns and merge into the same lymph node.

In recent years, there has been growing interest in the application of exogenous contrast agents to supplement the traditional strengths of optical coherence tomography (OCT). Here we present how indocyanine green (ICG), a common fluorescent contrast agent, can provide absorption and spectral contrast for OCT imaging in the mouse eye in vivo. We further demonstrate high stability of spectral contrast measurements for long term monitoring of contrast agents despite intensity fluctuations. This type of contrast-enhanced OCT may be able to provide similar information to ICG fluorescence angiography, but with the added benefit of depth-resolution and perfectly coregistered OCT intensity data.

We present a new OCT-based tissue dynamics/subcellular motion analysis method to visualize tissue dynamics, where we increase the functionality of OCT to be sensitive for tissue dynamics by utilizing rapid-time-sequence analysis of OCT signals. These analysis includes log intensity variance (LIV) and OCT time-correlation analysis (OCT decorrelation speed; OCDS). In addition to LIV and OCDS methods, attenuation coefficient (AC), birefringence, and degree of polarization uniformity (DOPU) analysis were performed. These methods used to visualize and quantify long-term tissue dynamics degradation of different tissue types such as dissected mouse liver and tumor spheroids. These methods were quantitative, so the time-course tissue dynamics degradation has been not only visualized as an image, but also quantitative analysis of the dynamics degradation were performed.

Optical coherence tomography (OCT) allows for imaging of fine structures below the surface of tissue based on inherent contrast from heterogeneity of optical refractive index. A contrast agent may be used when intrinsic contrast of a target in the sample is not enough. We synthesize magnetically-responsive nanorods whose reflectivity can be modulated by the orientation of a magnetic field and demonstrate their use in background-free OCT imaging. Because normal tissue does not respond to switching magnetic field, the signal from nanorods can be isolated from tissue.

A multimodal optical coherence tomography (MM OCT) combining microstructural cross-polarization (CP) imaging and compression OCT-elastography (OCE) was employed in this study. The research was carried out on the noninvasive and invasive subtypes of human breast cancer. This study demonstrates how CP OCT combined with OCTelastography identifies an example of DCIS cancer that progresses into invasive breast cancer. OCE images more clearly show the cross sections of the ducts filled with tumor cells for DCIS (high-contrast structures with clear boundaries and high stiffness values) surrounded by areas with lower stiffness corresponding to fibrous stroma regions. The regions of invasive breast cancer in OCE-scans look as zones with strongly increased stiffness, which well agrees with the histology. Percentage of pixels with different characteristic stiffness ("stiffness spectrum") in the OCTelastography images was assessed to quantitatively visualize stiffness of tumor. The demonstrated ability of MM OCT imaging for breast cancer subtypes differentiation and breast cancer margin assessment is important for improved managements of patients.

We demonstrate, to our knowledge for the first time, an integrated broadband master oscillator power amplifier (MOPA) module where amplified spontaneous emission (ASE) light from an 840-nm superluminescent diode (SLED) is amplified by a low-confinement, broadband 840-nm semiconductor optical amplifier (SOA) in order to generate power levels of more than 100 mW in free space. The SLED-SOA MOPA architecture is realized on a free-space, temperaturestabilized, micro-optical bench and integrated in a 14-pin butterfly module with an optical window output. The highlypolarized ASE light from the SLED is intrinsically aligned to the polarization of the SOA, thereby providing high-power amplified ASE light with an extinction ratio of more than 20 dB and with an optical bandwidth of more than 35 nm FWHM. Optimization of the ASE input signal and of the booster SOA design may either increase the optical bandwidth of the amplified ASE output signal or may also increase the output power levels to a regime of 200-300 mW.

Corneal cross-linking (CXL) has grown from an interesting concept to a practical clinical treatment for corneal ectatic disease globally in the past three decades. In both understanding the principle of how CXL proceeds and monitoring the clinical procedure, detection of structural changes during cornea CXL plays a significant role. This paper demonstrates a novel over-sampling nano-sensitive optical coherence tomography (osnsOCT) method, which is potential to detect nanoscale structural changes in various tissues, to simultaneously measure the structural variations during the corneal CXL treatment.

We demonstrate a novel light source for multi-modality imaging where three superluminescent diodes (SLEDs) are integrated on a free-space, temperature-stabilized, micro-optical bench in a standard 14-pin butterfly package. The light output of the three SLED chips is collimated by individual micro-optical collimation lenses and then spectrally and spatially combined in free space through dielectric edge filters before being coupled into a common HI-780 single-mode output fiber. The two SLEDs at 840 nm and 880 nm deliver a combined broadband spectrum with 120 nm bandwidth and 8.5 mW of output power for ultra-high-resolution optical coherence tomography (OCT) imaging with an axial resolution of ~4 microns in air. The third SLED at 750 nm is suitable for implementing eye tracking based on a scanning laser ophthalmoscope (SLO). Because of the free-space architecture, the polarization of all SLEDs is intrinsically aligned such that the UHR-OCT broadband source has a high PER of 20 dB across the entire spectrum.

The aim of this work is the creation of segmented data set consisting of optical coherence tomography (OCT) scans, which were taken of brain tumor tissue with different tumor infiltration rates. In an ongoing clinical study more than 140 human brain samples with different infiltration grades were recorded ex vivo with two OCT systems, a spectral domain OCT system and a swept-source OCT system that uses a 1310 nm Fourier domain mode locked laser. The histological analysis of the recorded samples builds the ground truth for labeling the corresponding OCT B-Scans. The segmented data set gained from this process will be used to train a classification algorithm, taking into account structural and optical properties such as the attenuation coefficient. In the future the classification algorithm together with a microscope integrated OCT system will be used for the in vivo identification of brain tumors as a guidance tool for the surgeon to increase tumor resection efficiency.

Motion artifacts and interference residuals limit the performance of conventional full-field optical coherence tomography (FF-OCT) for in vivo imaging. It is because piezoelectric translator-based phase-shifting method bring chromatic abberation with broadband light source and is wavelegnth-dependent. Many achromatic phase-shifters were designed and introduced additional mechanical vibrations into the imaging system. In this work, an achromatic phase-shifting mechanism was proposed with dual-channel FF-OCT. Based on a Linnik interferometer, a linear polarizer and a quarter-wave plate were employed in the reference arm to replace PZT and generate the circle polarized light beam. The light field reflected from the reference arm is supposed with the unpolarized light backscattered from the sample when the path difference is within the coherence length of the light source. With one phase difference of π/2 shifted by interference between the circle polarized light and unpolarized light. Two inteference beams were received by a pair of identical CCDs. With porposed numerical phase-shifting method based on Hilbert transform, the en face tomograms of sample will be reconstructed in a single-shot. The axial and lateral resolutions of the system are around 1.4µm and 0.8µm, respectively. Tomograms of Intel microchip were displayed with clear substructures. Three-dimensional miscrostructures of fresh and isolated mouse heart were obtained in video-rate. This article aims at producing fringe-free OCT images with imaging rate of 30fps.

Superluminescent diodes (SLDs) of spectral range 730 – 790 nm with strained single quantum-well (SQW) active layer and spatially single mode ridge waveguide were studied experimentally. SLDs with short active channels < 1000 μm have demonstrated broadband emission spectrum with median wavelength near 765 nm, FWHM of up to 60 nm and free space CW output power in the range 2 – 15 mW at 25°C. SLDs with longer active channels have demonstrated output of up to 150 mW and spectral half-width in the range 40 – 20 nm. TM mode was dominant in output emission.

Three types of light sources based on superluminescent diodes (SLDs) of NIR ranges 800 – 880 nm and 860 – 950 nm with spatially single mode active channels were studied. Light-emitting modules have demonstrated free space continuous wave (CW) output power of up to 150 mW and 75 mW ex single mode optical fiber (SMF), at spectral bandwidth of about 25 nm. Master Oscillator Power Amplifier (MOPA) system in which SLD of the first type was used as an active element of a power amplifier and blue-shifted SLD as a master oscillator permitted to broaden spectral bandwidth up to 50 nm at the same output optical power level. The estimated lifetime of these devices is more than 10000 hours. High power combined light source based on two MOPA systems with spectral FWHM of more than 100 nm was realized.

A method of numerical compensating of OCT image distortion provided by fluctuations of the distance to the object has been proposed and verified experimentally. The method is based on the analysis of inter A-scan phase shifts caused by micrometer-scale displacements, and the subsequent compensation of the displacements by phase-frequency correction in the spectral space. The efficiency of the method is demonstrated in model experiments with harmonic and random movements of a scattering object, as well as during in vivo imaging of the retina of the human eye.

In this communication, we present a method to measure the thickness of transparent media employing a low coherence interferometer and a multi-element array as a photo-detector. The multi-element array employed is part of a consumer-grade digital camera (< 0.5 k$). A two-beam interferometer is created by inserting the slab of a transparent material half-way through into the measurement beam. The method is evaluated on a thin microscope cover slip and on a thicker microscope glass slide.

In biomedical optics, Optical Coherence Tomography (OCT) is an emerging optical imaging modality during the last three decades. OCT can perform high resolution, cross-section imaging of the internal microstructure in biological tissues by measuring echoes of backscattered light. We have developed a broadband, high-resolution spectral domain OCT system whose central wavelength is 1300 nm with bandwidth ~400 nm. Theoretical axial resolution of the system is ~3.71 μm and experimentally we get ~5 μm in air. Furthermore, we will apply this system for nano-sensitive detection and visualization in varieties of biological tissues.