Liver Microcirculation
John H. Barker, Gary L. Anderson, Michael D. Menger in Clinically Applied Microcirculation Research, 2019
The principle of laser Doppler flowmetry is that an infrared laser with a wavelength of 780 ± 20 nm (1.6 mW) emits and penetrates up to 1 mm. Optical fibers of the flow probe conduct the laser beam to the tissue and the reflected light back to the photodetectors. Since the photons interact with moving red blood cells and stationary tissue cells, the portion of photons reflected and Doppler shifted indicates proportionally the moving microvascular blood volume and, by the frequency, the red blood cell velocity without indication of flow direction. A laser Doppler blood perfusion monitor and a flow probe available in different angles may be used for investigation of the liver surface following laparotomy.57 However, absolute measurements of blood flow are questionable so that relative measurements are recommended.58 Thus, LDF allows for monitoring tissue perfusion when a sufficient number of representative areas are scanned.59 For reflectance spectrophotometry in vivo, see previous section.
EM behavior when the wavelength is much smaller than the object
James R. Nagel, Cynthia M. Furse, Douglas A. Christensen, Carl H. Durney in Basic Introduction to Bioelectromagnetics, 2018
Optical mirrors are usually made of conductive metal coatings (such as aluminum) on a substrate such as glass. The reflection of optical waves from conductive coatings follows the same boundary conditions as for lower-frequency microwaves (see Section 3.3.1). The reflectivity R depends upon the conductivity of the coating but is generally around 90% for aluminum and higher for silver and gold. As before, the angle of reflection is equal to the angle of incidence. This is known as specular reflection. It makes ray tracing of the paths of the reflected waves from mirrors easily visualized. For example, Figure 4.7 shows parallel incident rays reflected from both a flat mirror and a spherical mirror. Since the spherical mirror surface is curved inward (concave), specular reflection causes the parallel rays to focus to a point halfway between the center of curvature and the mirror surface. (This is true for rays near the axis; for rays farther toward the periphery, some spreading of the focus spot, known as aberration, occurs.) Thus, for a concave spherical mirror, the focal length f is equal to one-half the radius of curvature R0, or f = R0 /2.
Modelling and analysis of skin pigmentation
Ahmad Fadzil Mohamad Hani, Dileep Kumar in Optical Imaging for Biomedical and Clinical Applications, 2017
A light reflectance model is a model used to describe the interaction of light with a surface. Typically, the model is formulated regarding the properties of the surface and the properties of the incident light. Figure 4.13 shows a frequently used physics-based reflection model of skin called the Dichromatic Reflection Model as applied in the reflections of dielectric non-homogeneous materials [66–68]. The Dichromatic Reflection Model describes the reflected radiance or light, L as an additive mixture of the light, LS reflected at the material's surface (surface reflection or surface reflectance) and the light, LB reflected from the material's body (diffuse reflection or diffuse reflectance): where e represents the viewing angle, g represents the phase angle and i represents the illumination direction angle. These are called photometric angles.
Influence of coating type, colour, and deployment timing on biofouling by native and non-native species in a marine renewable energy context
Published in Biofouling, 2022
Christopher R. Nall, Marie-Lise Schläppy, Elizabeth J. Cottier-Cook, Andrew J. Guerin
After a relatively short immersion time of 3 months, assemblages on the painted panels appeared to form two groups – the “darker” colours (red and black) and the “lighter” colours (white and yellow). When affected by colour, animal fouling taxa (exemplified by Ascidiella sp., and the NNS S. japonica and C. eumyota) were more abundant on darker surfaces, whilst algae (Chloropyhta spp.) were more abundant on the lighter surfaces. The tendency towards greater animal fouling on darker surfaces (Hurlbut 1993; Swain et al. 2006; Satheesh and Wesley 2010; Dobretsov et al. 2013) is likely to be at least partly mediated by negative phototaxis of many larvae during settlement (McDougall 1943; WHOI (Woods Hole Oceanographic Institute) 1952; Svane and Young 1989). This in contrast to active selection of lighter areas by some algal zoospores (Christie and Shaw 1968; Baynes 1999; Glasby 1999) and superior growth and adhesion strength of algae in lighter conditions (Hodson et al. 2000; Finlay et al. 2008). Lighter surfaces reflect more light over a wider range of wavelengths (Finlay et al. 2008); differences in surface reflectance may be more important than the colours as perceived by the human eye (Ells et al. 2016).
Mathematical and computational modeling for the determination of optical parameters of breast cancer cell
Published in Electromagnetic Biology and Medicine, 2021
Shadeeb Hossain, Shamera Hossain
Reflectance measurement allows scope for calibration of sensors and remote sensing (Di Girolamo 2003; Martonchik et al. 2000; Nicodemus et al. 1977; Schaepman-Strub et al. 2006). The concept of scattering parameter (S-parameter) is utilized to derive the reflectance magnitude. The scattering parameters correlate with reflection and transmission behavior of applied electromagnetic wave incident on dielectric malignant tissue sample (Salomatina et al. 2006). The S11 parameter is reflection measurement and explicates the evanescent and discontinuity behavior of polarized electromagnetic wave incident on boundary of dissimilar dielectric parameter. The nuance between Stoke’s relation and S-parameter includes the assumption of no EM absorption by system. However, a pragmatic representation has to peruse the absorption property because malignant tissues have a higher absorption property than its surrounding normal counterparts (Hossain 2020a, 2020b). The quantitative optical parameter distinction has prospective applications in technological advancement in optimized drug delivery procedures to target tumor sites or accurate diagnosis (Hossain 2018, 2020c; Hossain and Abdelgawad 2020; Hossain et al. 2019; Hu et al. 2018).
Retinal Pigment Epithelium Reflectivity at Leakage Site on Spectral-Domain Optical Coherence Tomography in Acute Central Serous Chorioretinopathy
Published in Seminars in Ophthalmology, 2021
Dmitrii S. Maltsev, Alexei N. Kulikov, Maria A. Burnasheva, Alina A. Kazak, Jay Chhablani
To minimize the effect of local factors on RPE reflectivity, a similar RPE area within the area of the NSD was chosen as a control site. The height of the NSD, presence of retinal nerve fiber layer and photoreceptor outer segments layer thickness above the leakage site, as well as the location of the leakage site within the NSD were taken into account when selecting a control site. To exclude the effects of individual factors such as optical media clarity on the evaluation of RPE reflectivity, we used a relative reflectivity index, described earlier.8 The relative reflectivity index was calculated as the ratio of RPE reflectivity in the area of interest (leakage site or control site) to the RPE reflectivity at the reference area. The reference area was defined as a normal RPE area outside the NSD on the same cross-sectional scan where the leakage or control site was displayed. The reference area was chosen avoiding large retinal vessels or thick part of retinal nerve fiber layer
Related Knowledge Centers
- Angle of Incidence
- Radiant Energy
- Reflection
- Angle of Incidence
- Radiant Flux
- Radiance
- Bidirectional Reflectance Distribution Function
- Opposition Surge
- Fresnel Equations
- Plane of Incidence
- Lambertian Reflectance