Application of Wideband Acoustic Immittance (WAI) in Assessment of the Middle Ear in Newborns, Children, and Adults
Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm in Advances in Audiology and Hearing Science, 2020
At the end of this chapter the readers should be able to: Explain Wideband Acoustic Immittance (WAI) and its similarities and differences to conventional tympanometry.Analyze WAI patterns in normal and different middle ear pathologies.Differentiate WAI patterns between different age groups and different middle ear pathologies.Define absorbance and reflectance.Compare WAI with tympanometric outcomes in normal ears and ears with different middle ear pathologies.Understand the pros and cons of WAI in the assessment of middle ear function.Identify the limitation of middle ear analysis techniques and identify areas for future research direction.
Retinal image enhancement and analysis for diabetic retinopathy assessment
Ahmad Fadzil Mohamad Hani, Dileep Kumar in Optical Imaging for Biomedical and Clinical Applications, 2017
Varied contrast in an image is characterised by spurious smooth variation of image intensities. Variation of image intensities is mainly due to the effect of illumination. Illumination determines the lightness of an image. Land showed that the relationship between reflectance and lightness is not linear but, generally can be approximated with cube root, square root and logarithmic functions [60]. Here, smooth variation of image intensities is modelled using a mathematical function where k and α are constants. The above function is a general function in which cube root and square root are obtained for α equal to (1/3) and (1/2). A smooth image intensity variation i(x) as a function of pixel's position x is mathematically formulated as
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.
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
Figure 5 is our active area of interest on this paper because it compares the graphical COMSOL simulation of Fresnel equation (for reflectance), analytical reflectance and mathematical Fresnel Equation (1) (to determine the critical angle of malignant tissue). The reflectance is measured across a range of incident angle 0–1.57 (radians) equivalent of 0–90°. As discussed earlier, S11 parameter is used to determine the reflectance by COMSOL Multiphysics (represented by asterisk in Figure 5). The shape of the graph is in good agreement with the analytical Fresnel equation. Note should be taken that the modified Fresnel equation (referred as Equation 1) is polarization independent but the analytical Fresnel equation (referred as Equation 8) is applicable for TE (S-polarization).
Residence time and mixing capacity of a rotary tablet press feed frame
Published in Drug Development and Industrial Pharmacy, 2021
Maren Zimmermann, Markus Thommes
The measurement was conducted in reflectance mode. Thereby the reflected light intensity was compared to the initial emitted light intensity. The ratio as a function of the wavelength was called spectra. In all cases, a white tablet consisting of the model formulation served as reference on which the system was calibrated a priori. Therefore, the conducted determination of the light intensity ratio defined as reflection rate R was a relative measurement. R was attenuated by the weight fraction of the UV-sensitive tracer (theophylline) (Figure 2, left). For further processing, the absorbance was calculated from the reflection rate R by using the Schuster–Kubelka–Munk equation (Equation (10)) at the maximum molar attenuation coefficient (272 nm). The equation was found for calculating absorption and scattering of light on solid layers [36].
Calibrating UVA reflectance photographs – standardisation using a low-cost method
Published in Journal of Visual Communication in Medicine, 2018
Overall the custom targets using magnesium oxide, plaster of Paris and carbon black, provide a cheap, and simple way to enable the taking of calibrated monochrome UVA reflectance photographs. By varying the relative amounts of magnesium oxide, plaster of Paris and carbon black it is possible to generate a wide range of reflectances. At this stage, it is only fair to highlight the drawbacks of this method as well. The targets described here are soft, and susceptible to damage and contamination if not handled carefully. However the same could be said of Spectralon® samples which are easily contaminated. There is a bump in the reflectance spectra of the lighter custom targets which leads to greater error in the average reflectance scores. While the method to make the custom targets is simple, differences in batches of the raw starting materials could lead to slight changes in the degree of reflectance of the final targets. Ideally, once made their reflectance spectra should be measured to ensure accuracy. This is relatively straightforward using a UV Visible spectrometer, which is a common piece of equipment in Analytical laboratories. The images here were captured as jpeg files, and as such have undergone a degree of in-camera processing. While some may choose to capture the images as RAW files (Solli, Andersson, Lenz & Kruse, 2005; Garcia, Dyer, Greentree, Spring & Wilsch, 2013), as long as the conditions under which the images are captured, and the lighting is kept constant, this is not an issue as was observed by the high degree of correlation observed in the UVA image.
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