Evaluation of expelled droplets through traditional Islamic face coverings.

BACKGROUND: Expelled droplet count is an important factor when investigating the efficacy of face coverings since higher droplet counts indicate an increased possibility of disease transmission for airborne viruses such as COVID-19. While there is some published work relating facemask style to expelled droplet count during speech, there is no published data regarding the effectiveness of traditional Islamic face coverings such as the ghutra and niqab commonly worn by men and women in the Arabian Peninsula. OBJECTIVES: Measure the effectiveness of worn traditional Islamic face coverings in reducing expelled droplet count during speech. DESIGN: Experimental study SETTING: Biomedical engineering department at a university in Saudi Arabia. MATERIALS AND METHODS: Using a previously described low-cost method for quantifying expelled droplets, this study compares droplet counts through commonly worn traditional Islamic face coverings and conventional three-ply surgical masks worn during speech. The device records scattered light from droplets (>5 µm diameter) as they pass through a laser light sheet (520 nm), and then video processing yields droplet counts. MAIN OUTCOME MEASURES: Percent reduction in the number of expelled droplets passing through face coverings during speech compared to no face covering MAIN OUTCOME MEASURES: 9-15 recorded samples per face covering (n=3) plus no face covering control (n=1) in three females. RESULTS: The average percent reduction for each mask type compared to no mask trial was 76% for the cotton ghutra, 93% for the niqab, and 95% for the surgical mask. The niqab and ghutra had relatively high variability in droplet reduction. CONCLUSIONS: Traditional Islamic face coverings block some expelled droplets, but at lower rates than surgical masks. High standard deviations within facemask groups with high variability in fit (i.e., the cotton ghutra) further denote the importance of fit in face covering effectiveness. Some protection from airborne viruses is likely with traditional Islamic face coverings compared to no mask, but the amount of protection depends on the fit of the face covering. LIMITATIONS: Detectable droplets limited to particles greater than 5 µm diameter with forward expulsion direction. CONFLICT OF INTEREST: None.

Scattering Angle Resolved Optical Coherence Tomography Detects Early Changes in 3xTg Alzheimer's Disease Mouse Model.

Purpose: Clinical intensity-based optical coherence tomographic retinal imaging is unable to resolve some of the earliest changes to Alzheimer's disease (AD) neurons. The aim of this pilot study was to demonstrate that scattering-angle-resolved optical coherence tomography (SAR-OCT), which is sensitive to changes in light scattering angle, is a candidate retinal imaging modality for early AD detection. SAR-OCT signal data may be sensitive to changes in intracellular constituent morphology that are not detectable with conventional OCT. Methods: In this cross-sectional study, retinas of a triple transgenic mouse model of AD (3xTg-AD) were imaged alongside age-matched control mice (C57BL/6J) using SAR-OCT. A total of 32 mice (12 control, 20 3xTg-Ad) at four ages (10, 20, 30, and 45 weeks) were included in this cross-sectional study, and three retinal feature sets (scattering, thickness, and angiography) were examined between the disease and control groups. Results: AD mice had significantly increased scattering diversity (lower SAR-OCT C parameter) at the earliest imaging time (10 weeks). Differences in the C parameter between AD and control mice were diminished at later times when both groups showed increased scattering diversity. AD mice have reduced retinal thickness compared to controls, particularly in central regions and superficial layers. No differences in vascular density or fractional blood volume between groups were detected. Conclusions: SAR-OCT is sensitive to scattering angle changes in a 3xTg-AD mouse model and could provide early-stage biomarkers for neurodegenerative diseases such as AD. Translational Relevance: Clinical OCT systems may be modified to record SAR-OCT images for non-invasive retinal diagnostic imaging of patients with neurodegenerative diseases such as AD.

Scattering-Angle-Resolved Optical Coherence Tomography of a Hypoxic Mouse Retina Model.

Several studies have noted a correlation between retinal degeneration and traumatic encephalopathy (TE) making the retina a leading candidate for detection and assessment. Scattering-angle-resolved optical coherence tomography (SAR-OCT) is a candidate imaging modality to detect sub-resolution changes in retinal microstructure. SAR-OCT images of murine retinas that experience a hypoxic insult-euthanasia by isoflurane overdose-are presented. A total of 4 SAR-OCT measurement parameters are reported in 6 longitudinal experiments: blood flow volume fraction, total retinal thickness, reflectance index, and scattering angle. As each mouse expires, blood flow volume fraction decreases, total retinal thickness increases, reflectance index decreases, and scattering angle diversity increases. Contribution of the retinal vasculature to scattering angle diversity is discussed. Results of this study suggest the utility of SAR-OCT to measure TE using scattering angle diversity contrast in the retina.

In situ process monitoring in selective laser sintering using optical coherence tomography.

Selective laser sintering (SLS) is an efficient process in additive manufacturing that enables rapid part production from computer-based designs. However, SLS is limited by its notable lack of in-situ process monitoring when compared to other manufacturing processes. We report the incorporation of optical coherence tomography into an SLS system in detail and demonstrate access to surface and sub-surface features. Video frame rate cross-sectional imaging reveals areas of sintering uniformity and areas of excessive heat error with high temporal resolution. We propose a set of image processing techniques for SLS process monitoring with OCT and report the limitations and obstacles for further OCT integration with SLS systems.

High-speed and high-sensitivity parallel spectral-domain optical coherence tomography using a supercontinuum light source.

The three most important metrics in optical coherence tomography (OCT) are resolution, speed, and sensitivity. Because there is a complex interplay between these metrics, no previous work has obtained the best performance in all three metrics simultaneously. We demonstrate that a high-power supercontinuum source, in combination with parallel spectral-domain OCT, achieves an unparalleled combination of resolution, speed, and sensitivity. This system captures cross-sectional images spanning 4 mm×0.5 mm at 1,024,000 lines/s with 2×14 µm resolution (axial×transverse) at a sensitivity of 113 dB. Imaging using the proposed system is demonstrated on highly differentiated human bronchial epithelial cells to capture and spatially localize ciliary dynamics.