Automatic segmentation of layers in chorio-retinal complex using Graph-based method for ultra-speed 1.7 MHz wide field swept source FDML optical coherence tomography.

The posterior segment of the human eye complex contains two discrete microstructure and vasculature network systems, namely, the retina and choroid. We present a single segmentation framework technique for segmenting the entire layers present in the chorio-retinal complex of the human eye using optical coherence tomography (OCT) images. This automatic program is based on the graph theory method. This single program is capable of segmenting seven layers of the retina and choroid scleral interface. The graph theory was utilized to find the probability matrix and subsequent boundaries of different layers. The program was also implemented to segment angiographic maps of different chorio-retinal layers using "segmentation matrices." The method was tested and successfully validated on OCT images from six normal human eyes as well as eyes with non-exudative age-related macular degeneration (AMD). The thickness of microstructure and microvasculature for different layers located in the chorio-retinal segment of the eye was also generated and compared. A decent efficiency in terms of processing time, sensitivity, and accuracy was observed compared to the manual segmentation and other existing methods. The proposed method automatically segments whole OCT images of chorio-retinal complex with augmented probability maps generation in OCT volume dataset. We have also evaluated the segmentation results using quantitative metrics such as Dice coefficient and Hausdorff distance This method realizes a mean descent Dice similarity coefficient (DSC) value of 0.82 (range, 0.816-0.864) for RPE and CSI layer.

Exploring the impact of PVC and PVA microplastics on zebrafish tissue using multi-spectral imaging, Optical Coherence Tomography (OCT) and biospeckle OCT (bOCT).

Plastics are widely used in industry and households, but improper disposal has caused their accumulation in aquatic systems worldwide. As a result, mechanical and photochemical processes break down these plastics into microplastics or nano plastics, posing a severe threat to marine organisms and humans as they enter the food chain. This study investigates the effect of Polyvinyl chloride (PVC) and Polyvinyl alcohol (PVA) microplastics in zebrafish by using multi-spectral imaging (MSI), Optical Coherence Tomography (OCT), and Biospeckle OCT (bOCT). These techniques allow for long-term studies in the fish without invasive procedures in real-time. Zebrafish were exposed to Nile red labeled PVC and PVA for 21 days with 500mg/L concentration. Image acquisition and analysis were performed every five days till the end of the study. MSI images revealed deposition of microplastics in the gills region of the fish; some diffused deposition was seen throughout the body in the PVA group towards the end of the experiment. The effect of these MPs on the structure of the gills and their exact location was determined by capturing OCT images. bOCT was used to determine the average speckle contrast for all the OCT images to determine the change in biological activity within the gills region. An increase in bioscpeckle contrast was observed for the MPs treated groups compared to the control group. PVC appeared to cause a more considerable rise in activity compared to PVA. The results indicated that the MPs exert stress on the gills and increase activity within the gills, possibly due to the blockage of the gills and disruption of the water filtration process, which could be monitored non-invasively only by using bOCT. Overall, our study demonstrates the usefulness of non-invasive, robust techniques like MSI, bOCT, and biospeckle for long-term zebrafish studies and real-time analyses.

Albumin-PEG-Based Biomaterial for Laser-Tissue Soldering and Its Real-Time Monitoring With Swept-Source Optical Coherence Tomography.

BACKGROUND AND OBJECTIVES: The study presents a noninvasive, real-time monitoring technique for the cross-sectional imaging of the laser-tissue soldering process with a swept-source optical coherence tomography (SSOCT) system. The study also aims at performing a comparative study of the laser-tissue soldering (LTS) process using optimized compositions of albumin as solder biomaterials. STUDY DESIGN/MATERIALS AND METHODS: The experimental study was conducted both ex vivo and in vivo to assess the superiority of the LTS process over conventional methods using a noninvasive imaging tool. In our attempt to combine the two techniques into one diagnostic tool, we have used the SSOCT system for a thoroughgoing investigation of the process in real-time. Laser-assisted tissue soldering was performed using a pulsed near-infrared (NIR) laser with a central wavelength of 980 nm, an output power of 5 W, and beam diameter (1/e 2 ) of 6 mm. Here, the SSOCT system has been utilized to observe and analyze the transitions taking place in real-time without disrupting the process. For the comparative study, we have used serum albumin in a 70% w/v concentration and albumin-PEG conjugate in a 6:1 ratio as soldering materials. Different stages of the laser interaction process were monitored with OCT B-scans of the incision area. Also, the basis of biomaterial-tissue interaction was studied with the help of Fourier-transform infrared spectroscopy (FTIR) analysis of the soldering materials. RESULTS: FTIR spectrum alludes to the fact that the intertwining of the soldering biomaterial with tissue collagen creates adhesion. Biomaterial serum albumin with 70% w/v concentration as soldering material demonstrates complete sealing of tissue at the incision with 3 minutes of laser irradiation. SSOCT B-scans have been useful in imaging the incision noninvasively at different stages. CONCLUSION: Both ex vivo and in vivo demonstration of the LTS process were presented with a clinical resemblance. OCT can be of great value to determine the wound contraction in case of incisional wounds or sealed wounds produced by the LTS procedure. Also, volumetric measurements of percentage reduction in wound area can be done with OCT. SSOCT system can be a potential imaging modality for real-time noninvasive imaging of surgical procedures like LTS. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Real-time assessment and characterization of immobilized lipase onto a natural matrix and qualitative reaction kinetic studies using swept-source optical coherence tomography.

The current study presents a method based on Optical Coherence Tomography (OCT) for non-destructive, real-time analysis and portrayal of immobilization efficacy for lipase on a natural matrix namely, eggshell. Subsequently, qualitative biochemical reaction kinetics of immobilized lipase was also studied. Successful immobilization of lipase on eggshell was confirmed by the presence of a clear peak in 'A' scan of OCT image. From immobilization kinetics it is clearly observed that the thickness of the highest peak of the A-scan increases significantly and peak intensity saturated after 90 min of incubation. Hydrolysis of oil using immobilized lipase indicated that the release of free fatty acids increased up to 8 h during reaction and the result was in accordance with the 'B' scan data of the OCT system. Changes in scattering coefficient-based analysis were performed with respect to incubation time to showcase the immobilization process and hydrolysis reaction of lipase. Scanning electron microscope analysis with smoother surface indicated presence of lipase on eggshell matrices, with no further change after oil hydrolysis.