In this study, a Q-switch pumped supercontinuum laser (QS-SCL) is used as a light source for in vivo imaging via ultrahigh-resolution optical coherence tomography and angiography (UHR-OCT/OCTA). For this purpose, an OCT system based on a spectral-domain detection scheme is constructed, and a spectrometer with a spectral range of 635 − 875 nm is designed. The effective full-width at half maximum of spectrum covers 150 nm, and the corresponding axial and transverse resolutions are 2 and 10 µm in air, respectively. The relative intensity noise of the QS-SCL and mode-locked SCL is quantitatively compared. Furthermore, a special processing algorithm is ...

Optical coherence tomography (OCT) angiography (OCTA) has been actively studied as a noninvasive imaging technology to generate retinal blood vessel network maps for the diagnoses of retinal diseases. Given that the uses of OCT and OCTA have increased in the field of ophthalmology, it is necessary to develop retinal phantoms for clinical OCT for product development, performance evaluation, calibration, certification, medical device licensing, and production processes. We developed a retinal layer-mimicking phantom with microfluidic channels based on microfluidic fabrication technology using polydimethylsiloxane (PDMS) and titanium dioxide (TiO 2 ) powder. We implemented superficial and deep retinal vessels using microfluidic channels. In ...

Quantitative velocity estimations in optical coherence tomography requires the estimation of the axial and lateral flow components. Optical coherence tomography measures the depth resolved complex field reflected from a sample. While the axial velocity component can be determined from the Doppler shift or phase shift between a pair of consecutive measurements at the same location, the estimation of the lateral component for in vivo applications is still challenging. One approach to determine lateral velocity is multiple simultaneous measurements at different angles. In another approach the lateral component can be retrieved through repeated measurements at (nearly) the same location by an ...

Intravascular optical coherence tomography (IVOCT) lumen-based computational flow dynamics (CFD) enables physiologic evaluations such as of the fractional flow reserve (FFR) and wall sheer stress. In this study, we developed an accurate, time-efficient method for extracting lumen contours of the coronary artery. The contours of cross-sectional images containing wide intimal discontinuities due to guide wire shadowing and large bifurcations were delineated by utilizing the natural longitudinal lumen continuity of the arteries. Our algorithm was applied to 5931 pre-intervention OCT images acquired from 40 patients. For a quantitative comparison, the images were also processed through manual segmentation (the reference standard) and ...

In vivo visualization and quantification of choriocapillaris vascular anatomy is a fundamental step in understanding the relation between choriocapillaris degradation and atrophic retinopathies, including geographic atrophy. We describe a process utilizing ultrahigh-speed swept-source optical coherence tomography and a custom-designed “local min-max normalized masking” algorithm to extract in vivo anatomical metrics of the choriocapillaris. We used a swept-source optical coherence tomography system with a 1.6 MHz A-scan rate to image healthy retinas. With the postprocessing algorithm, we reduced noise, optimized visibility of vasculature, and skeletonized the vasculature within the images. These skeletonizations were in 89 % 89% agreement with those made ...

Polarization-sensitive optical coherence elastography (PS-OCE) is developed for improved tissue discrimination. It integrates Jones matrix-based PS-optical coherence tomography (PS-OCT) with compression OCE. The method simultaneously measures the OCT intensity, attenuation coefficient, birefringence, and microstructural deformation (MSD) induced by tissue compression. Ex vivo porcine aorta and esophagus tissues were investigated by PS-OCE and histological imaging. The tissue properties measured by PS-OCE are shown as cross-sectional images and a three-dimensional (3-D) depth-trajectory plot. In this trajectory plot, the average attenuation coefficient, birefringence, and MSD were computed at each depth, and the trajectory in the depth direction was plotted in a 3-D feature ...

We observed that the polarization state of light after round-trip propagation through a birefringent medium frequently aligns with the employed input polarization state ‘mirrored’ by the horizontal plane of the Poincaré sphere. We explored the predisposition for this mirror state and evidence that it constrains the evolution of polarization states as a function of the round-trip depth into weakly scattering birefringent samples, as measured with polarization-sensitive optical coherence tomography (PS-OCT). Combined with spectral variations in the polarization state transmitted through system components, we demonstrate how this constraint enables measurement of depth-resolved birefringence using only a single input polarization state, which ...

We longitudinally imaged both the superficial and deep cortical microvascular networks in brains of healthy mice and in a mouse model of stroke in vivo 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. Following microprism implantation, we imaged the mice for 28 days and found that that it took around 15 days for both the superficial and deep cortical microvessels to recover from the implantation surgery. After the brains recovered, we introduced ischemic strokes by ...

This feature issue of Biomedical Optics Express represents a cross-section of the most recent work in tissue optics, including exciting developments in tissue optical clearing, deep tissue imaging, optical elastography, nanophotonics in tissue, and therapeutic applications of light, amongst others. A collection of 33 papers provides a comprehensive overview of current research in tissue optics, much of it inspired and informed by the pioneering work of Prof. Valery Tuchin. The issue contains three invited manuscripts and several mini-reviews that we hope will benefit researchers in this exciting area.

A combination of multispectral photoacoustic microscopy (PAM) and optical coherence tomography (OCT) by a single light source was previously realized discretely; however, this is unfavorable for visualizing vital physiological and pathological activities in vivo . Here, a co-impulse dual-mode imaging system that simultaneously enables multispectral PAM and OCT using a megahertz supercontinuum pulse laser in vivo is presented. The 500–600 nm band is used for functional PAM imaging, which can flexibly switch between different wavelengths, while the 600–840 nm band is selected for OCT imaging. A mimicking phantom experiment and in vivo imaging of normal and melanoma mouse ears ...

We demonstrate experimentally ghost optical coherence tomography using a broadband incoherent supercontinuum light source with shot-to-shot random spectral fluctuations. The technique is based on ghost imaging in the spectral domain where the object is the spectral interference pattern generated from an optical coherence tomography interferometer in which a physical sample is placed. The axial profile of the sample is obtained from the Fourier transform of the correlation between the spectrally resolved intensity fluctuations of the supercontinuum and the integrated signal measured at the output of the interferometer. The results are in excellent agreement with measurements obtained from a conventional optical ...

This paper reports on progress in the analysis of time-domain optical coherence tomography (OCT) applied to the dimensional metrology of through-silicon vias (TSVs), which are vertical interconnect accesses in silicon, enabling three-dimensional (3D) integration in microelectronics, and estimates the deviations from earlier, simpler models. The considered TSV structures are 1D trenches and circular holes etched into silicon with a large aspect ratio. As a prerequisite for a realistic modeling, we work with spectra obtained from reference interferograms measured at a planar substrate, which fully includes the dispersion of the OCT apparatus. Applying a rigorous modal approach, we estimate the differences ...

A custom-built ultrahigh-resolution optical coherence tomography (UHR-OCT) system and fluorescein staining were employed for investigation of a scopolamine induced dry eye mouse model. Acquired data was used to evaluate common and complementary findings of the two modalities. Central corneal thickness as measured by UHR-OCT increased significantly over the study period of 24 hours, from 89.0 ± 3.57 µm to 92.2 ± 4.07 µm. Both techniques were able to show corneal lesions with a large range of severity. Localized fluorescein staining was detected in 5% and diffuse staining in 45% of cases where no epithelial damage was visible with ...

n biological tissue, longer near-infrared wavelengths generally experience less scattering and more water absorption. Here we demonstrate an optical coherence tomography (OCT) system centered at 2.1 microns, whose bandwidth falls in the 2.2 micron water absorption optical window, for in vivo imaging of the rodent brain. We show in vivo that at 2.1 microns, the OCT signal is actually attenuated less in cranial bone than at 1.3 microns, and is also less susceptible to multiple scattering tails. We also show that the 2.2 micron window enables direct spectroscopic OCT assessment of tissue water content. We ...

Quantitative analysis of the peripapillary retinal layers and capillary plexuses from optical coherence tomography (OCT) and OCT angiography images depend on two segmentation tasks – delineating the boundary of the optic disc and delineating the boundaries between retinal layers. Here, we present a method combining a neural network and graph search to perform these two tasks. A comparison of this novel method’s segmentation of the disc boundary showed good agreement with the ground truth, achieving an overall Dice similarity coefficient of 0.91 ± 0.04 in healthy and glaucomatous eyes. The absolute error of retinal layer boundaries segmentation in the ...

We describe the details of a multimodal retinal imaging system which combines adaptive optics (AO) with an integrated scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT) imaging system. The OCT subsystem consisted of a swept-source, Fourier-domain mode-locked (FDML) laser, with a very high A-scan rate (1.6 MHz), whose beam was raster scanned on the retina by two scanners—one resonant scanner and one galvanometer. The high sweep rate of the FDML permitted the SLO and OCT to utilize the same scanners for in vivo retinal imaging and, unlike existing multimodal systems, concurrently acquired SLO frames and OCT volumes ...

We demonstrate a calibration-free time-stretch optical coherence tomography (TS-OCT), based on an optical higher order dispersion compensation scheme, which substitutes the digital calibration with optical dispersion compensation. As a result, the acquired raw data can directly perform the Fourier transform, and data processing time is greatly reduced by 82%, compared with the digital calibration. Moreover, because of the high-sensitivity and calibration-free characteristics, the high-order dispersion compensation-based TS-OCT can increase sensitivity roll-off by 2.6 times to 6.91 mm/dB and effective imaging depth by 14.2% to 16 mm. The in vivo biological tissue imaging has been demonstrated, with ...

We present mid-infrared (MIR) supercontinuum generation in polarization-maintained ZBLAN fibers pumped by 2 µm femtosecond pulses from a Tm:YAP regenerative amplifier. A stable supercontinuum that spreads from 380 nm to 4 µm was generated by coupling only 0.5 µJ pulse energy into an elliptical core ZBLAN fiber. The supercontinuum was characterized using cross-correlation frequency-resolved optical gating (XFROG). The complex structure of the XFROG trace due to the pulse-to-pulse spectrum instability have been fixed by reducing the length of the applied fibers or improving the quality of the incident pulse spectrum

We present a polarization-sensitive (PS) extension for bright- and dark-field (BRAD) optical coherence tomography imaging. Using a few-mode fiber detection scheme, the light backscattered at different angles is separated, and the BRAD images of tissue scattering are generated. A calibration method to correct for the fiber birefringence is proposed. Since particle scattering profiles are polarization dependent, a PS detection extends the capabilities for investigating the scattering properties of biological tissues. Both phantoms consisting of different-sized microparticles and a brain tissue specimen were imaged to validate the system performance and demonstrate the complementary image contrast.

A novel dual beam Optical Coherence Tomography (OCT) instrument has been developed for high velocity flow measurement, principally in microfluidics applications. The scanned dual beam approach creates a pair of image-frames separated by a small spatiotemporal offset. Metre-per-second flow measurement is achieved by rapid re-imaging by the second beam allowing for particle tracking between each image-frame of the pair. Flow at 1.06 m/s using a single optical access port has been measured, more than two orders of magnitude larger than previously reported OCT systems, at centimetre depth and with millimetre scale depth of field within a microfluidic chip ...

Voice disorders affect a large number of adults in the United States, and their clinical evaluation heavily relies on laryngeal videostroboscopy, which captures the medial-lateral and anterior-posterior motion of the vocal folds using stroboscopic sampling. However, videostroboscopy does not provide direct visualization of the superior-inferior movement of the vocal folds, which yields important clinical insight. In this paper, we present a novel technology that complements videostroboscopic findings by adding the ability to image the coronal plane and visualize the superior-inferior movement of the vocal folds. The technology is based on optical coherence tomography, which is combined with videostroboscopy within the ...