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Wearable Sensors for Blood Perfusion Monitoring in Patients with Diabetes Mellitus
Published in Andrey V. Dunaev, Valery V. Tuchin, Biomedical Photonics for Diabetes Research, 2023
Evgenii A. Zherebtsov, Elena V. Zharkikh, Yulia I. Loktionova, Angelina I. Zherebtsova, Viktor V. Sidorov, Alexander I. Krupatkin, Andrey V. Dunaev
The name of the method “laser Doppler flowmetry” reflects its basic ideas. For diagnostic purposes, the probing tissue area is exposed to laser radiation, and the laser beam reflected by the tissue is analyzed based on the extraction of the signal frequency (proportional to the particle velocity in the microvasculature) from the Doppler shift. This makes it possible to register microvascular changes in the blood or lymph flow using the flowmetry technique [10].
Orders Norzivirales and Timlovirales
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
Jeremiah J. Gassensmith’s team recently proposed a concept of the PhotoPhage, a Qβ VLP-based photothermal therapeutic agent (Shahrivarkevishahi et al. 2021). The design was based on covalent conjugation of 212 water soluble near-infrared absorbing croconium dyes to lysine residues on the VLP surface of Qβ, which turned it to a powerful NIR-absorber with photothermal efficiencies exceeding that of gold nanostructures. This PhotoPhage system generated heat upon 808 nm NIR laser radiation and caused significant cellular cytotoxicity that prevented the progression of primary tumors in mice. Moreover, the PhotoPhage acted simultaneously as an immunoadjuvant that promoted maturation of dendritic cells, triggered T lymphocyte cells, and reduced suppressive T regulatory cells, leading to effective suppression of primary tumors, reducing lung metastases, and increasing survival time (Shahrivarkevishahi et al. 2021).
Laser Photocoagulation Principles
Published in John P. Papp, Endoscopie Control of Gastrointestinal Hemorrhage, 2019
Figure 7 depicts the two important cases of laser light entering the human eye. When a laser beam travels directly from its source into the eye, it is focused to a very tiny spot on the retinal surface. This concentration of energy can cause thermal and/or mechanical damage. It is used to advantage by the ophthalmologist to perform microcoagulation of retinal vessels. Direct intrabeam viewing of greater than 10 mW of laser radiation can be damaging to the retina. Laser coagulation of 100 W implies 10,000 times the power of this threshold level. Once the laser radiation is inserted into an optical fiber, its hazard level drops significantly. For this reason, clinical systems should not be designed with open beams issuing directly from the laser generator source. They should be coupled into the fiber cables before being available to the clinical staff in order to avoid inadvertent retinal damage.
Determination of Micropulse Modes with Targeted Damage to the Retinal Pigment Epithelium Using Computer Modeling for the Development of Selective Individual Micropulse Retinal Therapy
Published in Current Eye Research, 2022
Elena V. Ivanova, Pavel L. Volodin, Alexey V. Guskov
Up until now, the diagnostic methods used in ophthalmology, such as the AF method and spectral OCT, do not quantify the harmful effect in vivo. The degree of laser radiation exposure to eye structures has only been assessed in histological studies using animals. Using the selectivity concept introduced in this paper, it is possible to quantify damage of the RPE and the adjacent structures for different laser modes. The micropulse mode (50 µs, 2.4% duty cycle, 10 ms) results in selectivity and efficiency values of greater than 67% within a certain range of micropulse power and is preferable for use in the fovea avascular zone. The results of the treatment in patients with acute and chronic CSCR, employing similar micropulse parameters to the Navilas 577s laser system, have been presented previously.41,42
Assessing the impact of low level laser therapy (LLLT) on biological systems: a review
Published in International Journal of Radiation Biology, 2019
Ruwaidah A. Mussttaf, David F. L. Jenkins, Awadhesh N. Jha
Laser is a device, which produces intense, monochromatic, coherent, and highly collimated beam of light (Fonseca et al. 2010). Laser light has quite pure frequency, which makes it useful for biomedical applications (Ratkay-Traub et al. 2001). Laser therapy involves visible red and near infrared (NIR) portions of the electromagnetic spectrum (390–1600 nm and 1013–1015 HZ) because researchers have shown that these portions of the spectrum have been absorbed highly by the biological systems and bring about a beneficial therapeutic effects in living tissues (Hawkins et al. 2005). According to the portion of the spectrum (wavelength) that strikes the tissue and the intensity (power density or irradiance) of laser radiation, the photobiological impacts of laser therapy on tissue are different that lead to divide the laser therapy into two classes (Hawkins and Abrahamse 2006). Class I, which refers to radiation of wavelengths ranges (<390 nm and >10,600 nm) and high power and intensity levels, are used for ablation, cutting and sterilization, because of its thermal effect. Class II, which refers to radiation of wavelength ranges (390–10,600 nm), levels of power (10−3 to 10−1 W) and intensity (10−1 to 10° W/cm2) and a dose of 10−2 to 102 J/cm2 (Posten et al. 2005).
Summary of numerical analyses for therapeutic uses of laser-activated gold nanoparticles
Published in International Journal of Hyperthermia, 2018
Heat transfer and thermal damage models help estimate the influence of laser radiation on biological tissue. While insufficient radiation energy decreases the treatment efficacy, high temperatures are harmful to surrounding healthy tissue. Moreover, the optical properties change with temperature, and thus, the use of Pennes' bio-heat equation can provide feedback for time-resolved light propagation effects. Modified versions of this equation were published many times, but they are not extensively used in PTT simulations and could provide an inspiration for further research.