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Polarization states of laser beam: figure was reproduced from the Encyclopedia of Laser Physics and Technology and is used with permission by RP Photonics Consulting GmbH
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![FIG. 5: Origin of Astigmatism of laser beam Top and side view [10].](profile/Muhammad-Zeeshan-Khalid/publication/303993089/figure/fig3/AS:373441405440002@1466046777277/Origin-of-Astigmatism-of-laser-beam-Top-and-side-view-10_Q320.jpg)
![FIG. 6: Output optical power vs. diode current curve [13].](profile/Muhammad-Zeeshan-Khalid/publication/303993089/figure/fig4/AS:373441405440003@1466046777315/Output-optical-power-vs-diode-current-curve-13_Q320.jpg)
After the discovery of laser therapy it was realized it has useful application of wound healing and reduce pain, but due to the poor understanding of the mechanism and dose response this technique remained to be controversial for therapeutic applications. In order to understand the working and effectiveness different experiments were performed to d...
Context in source publication
Context 1
... this property of Laser coexist with other properties of Laser radiation, so it is important to know about the polarization state of Laser radiation. Laser radiation can be polarized in a specific way (Horizontal, Linear polarization, etc.) by the use Figure 4 illustrates the different polarization states of laser radiation for a beam of few pulse cycles propagating from left to right. ...
Citations
... Spatial coherence describes a relationship between the phase of a laser beam at two different geometrical points, whereas temporal coherence describes a relationship between the phase of a laser beam at a specific point but at different times. The coherence property allows lasers to have a bandwidth of 1 nm or less [26]. Laser devices produce light with different coherence lengths depending on the exact type of lasing medium. ...
This chapter delves into the biophysical principles and safety concerns associated with the use of photobiomodulation (PBM) for brain applications. It provides a comprehensive understanding of the different components involved in designing and implementing PBM treatments. Section 2.1 discusses various light sources used in PBM, including lasers, LEDs, and other types of devices. The advantages and disadvantages of each type are presented, along with their specific applications in brain PBM. Section 2.2 outlines the dosimetry and treatment parameters involved in PBM, including coherence, wavelength, power, irradiance, fluence, radiant energy, pulse mode of operation, beam area, beam profile, irradiation time, and treatment repetition regimen. Each parameter is described in detail, with an emphasis on their significance and influence on treatment outcomes. Section 3 focuses on the safety concerns related to brain PBM. The discussion begins with an overview of laser classes (Sect. 3.1), which categorize lasers based on their potential to cause biological harm. Section 3.2 addresses thermal effects and concerns, detailing the potential risks and precautionary measures associated with PBM-induced heating. Lastly, Sect. 3.3 presents the safety profiles of PBM in pre-clinical and clinical studies, highlighting the general safety and tolerability of the technique in various applications. This chapter provides readers with the necessary background knowledge to understand the principles, parameters, and safety aspects of brain PBM, ensuring a solid foundation for further exploration of the field.
... Several studies, either in vivo and/or in vitro, have focused on implementing native fluorescence or autofluorescence (AF) in medical applications in the ultraviolet (UV)-visible and near-infrared (IR) spectral range when medical or biological substrates are excited with light at a suitable wavelength [4][5][6][7][8][9][10]. The strict relationship between several endogenous fluorophores and living systems' morphofunctional properties influences the AF emission features. ...
... The mechanism of laser beam interaction at the cellular and tissue level has been studied [9]. The aim was to understand the operation and effectiveness of the laser beam effect at the cellular and tissue levels. ...
... The aim was to understand the operation and effectiveness of the laser beam effect at the cellular and tissue levels. Various laser sources and the dosimetry principles of laser therapy applications have been reviewed [9]. Fs laser applications for biopreservation and profound implications for surgery and cell isolation have been investigated. ...
In in vitro methods and cell culture models, femtosecond (fs) laser interaction has been employed to assess its effect on the proliferation and morphology of human skin fibroblasts. We cultured a primary human skin fibroblast cell line on a glass plate, passages 17–23. The cells were irradiated with a 90-fs laser at a wavelength of 800 nm and a repetition rate of 82 MHz. The target received an average power of 320 mW for 5, 20, and 100 s, corresponding to the radiation exposures of 22.6, 90.6, and 452.9 J/cm², respectively. Using a laser scanning microscopy technique, the photon densities were measured to be 6.4 × 10¹⁸, 2.6 × 10¹⁹, and 1.3 × 10²⁰ photons/cm² in a spot area of 0.07 cm²; the recorded spectra were obtained from the laser interaction after 0.00, 1.00, 25.00, and 45.00 h. The cell count and morphological changes showed that the cultured cells were affected by laser irradiation under photon stress; some fibroblasts were killed, while others were injured and survived. We discovered evidence of the formation of several coenzyme compounds, such as flavin (500–600 nm), lipopigments (600–750 nm), and porphyrin (500–700 nm). This study is motivated by the future development of a novel, ultra-short fs laser system and the need to develop a basic in vitro understanding of photon–human cell interaction. The cell proliferation indicated that cells are partly killed or wounded. The exposure of fibroblasts to fs laser fluence up to 450 J/cm² accelerates cell growth of the viable residual cell.
... Silica is generally recognized as safe (Food and Drug Administration, FDA). Silica, in the form of Cornell dots (C dots), received FDA approval for stage 1 human clinical trials for targeted molecular imaging [11,21]. Silica particles have been described by He et al. as drug carriers for poorly soluble drugs and gene delivery, for both viral and nonviral systems [22]. ...
Although optical hyperthermia could be a promising anticancer therapy, the need for high concentrations of light-absorbing metal nanoparticles and high-intensity lasers, or large exposure times, could discourage its use due to the toxicity that they could imply. In this article, we explore a possible role of silica microparticles that have high biocompatibility and that scatter light, when used in combination with conventional nanoparticles, to reduce those high concentrations of particles and/or those intense laser beams, in order to improve the biocompatibility of the overall procedure. Our underlying hypothesis is that the scattering of light caused by the microparticles would increase the optical density of the irradiated volume due to the production of multiple reflections of the incident light: the nanoparticles present in the same volume would absorb more energy from the laser than without the presence of silica particles, resulting either in higher heat production or in the need for less laser power or absorbing particles for the same required temperature rise. Testing this new optical hyperthermia procedure, based on the use of a mixture of silica and metallic particles, we have measured cell mortality in vitro experiments with murine glioma (CT-2A) and mouse osteoblastic (MC3T3-E1) cell lines. We have used gold nanorods (GNRs) that absorb light with a wavelength of 808 nm, which are conventional in optical hyperthermia, and silica micropar-ticles spheres (hereinafter referred to as SMSs) with a diameter size to scatter the light of this wavelength. The obtained results confirm our initial hypothesis, because a high mortality rate is achieved with reduced concentrations of GNR. We found a difference in mortality between CT2A cancer cells and cells considered non-cancer MC3T3, maintaining the same conditions, which gives indications that this technique possibly improves the efficiency in the cell survival. This might be related with differences in the proliferation rate. Since the experiments were carried out in the 2D dimensions of the Petri dishes, due to sedimentation of the silica particles at the bottom, whilst light scattering is a 3D phenomenon, a large amount of the energy provided by the laser escapes outside the medium. Therefore, better results might be expected when applying this methodology in tissues, which are 3D structures, where the multiple reflections of light we believe will produce higher optical density in comparison to the conventional case of no using scattering particles. Accordingly, further studies deserve to be carried out in this line of work in order to improve the optical hyperthermia technique. Citation: Casanova-Carvajal, O.; Zeinoun, M.; Urbano-Bojorge, A.L.; Bacha, F.; Livi, J.S.; Agudo, E.; Vargas, G.; Ramos, M.; Martínez-Murillo, M.; Serrano-Olmedo1, J.J. The Use of Silica Microparticles to Improve the Efficiency of Optical Hyperthermia (OH). Int. J. Mol. Sci. 2021, 22, 5091.
... Although cells exhibit a very distinct irradiation sensitivity, the phototoxicity increases dramatically with decreasing irradiation wavelength. 36 Infrared light, as long as we do not pass the cellular thermal threshold through which apoptosis and destruction are induced, is safe. Nevertheless, ultraviolet light is mostly used for light-curing photopolymerization on stereolithographic bioprinting and has been reported to damage the DNA of cells. ...
Biofabrication technologies that use light for polymerization of biomaterials have made
significant progress in the quality, resolution, and generation of precise complex tissue
structures. In recent years, the evolution of these technologies has been growing along
with the development of new photocurable resins and photoinitiators that are biocompatible
and biodegradable with bioactive properties. Such evolution has allowed the progress of a
large number of tissue engineering applications. Flexibility in the design, scale, and
resolution and wide applicability of technologies are strongly dependent on the
understanding of the biophysics involved in the biofabrication process. In particular,
understanding cell–light interactions is crucial when bioprinting using cell-laden
biomaterials. Here, we summarize some theoretical mechanisms, which condition cell
response during bioprinting using light based technologies. We take a brief look at the
light–biomaterial interaction for a better understanding of how linear effects
(refraction, reflection, absorption, emission, and scattering) and nonlinear effects
(two-photon absorption) influence the biofabricated tissue structures and identify the
different parameters essential for maintaining cell viability during and after
bioprinting.
... It is the class 3B laser therapy with wavelength 600-950 nm, power less than 500mW and depth of penetration 0.5-2 cm. [12][13][14] However, the effectivity of LLLT for CTS still debatable. Bekhet et al. 15 reported that LLLT improved the strength of hand grip but not the pain, hand function, and electrophysiologic parameters. ...
Carpal tunnel syndrome (CTS) is the most common neuropathy compression syndrome. The effectiveness of low-level laser therapy (LLLT) as one of the conservative therapy for CTS is still debatable. High-intensity laser therapy (HILT) is developed with higher energy and deeper tissue penetration than LLLT. This study aimed to compare the effect of HILT and LLLT on sensory and motoric electrophysiologic parameters in moderate CTS patients. This was an experimental randomized pre and post-test group study. Sixteen patients (fifteen females and one male) with moderate CTS were randomly assigned into two groups. The HILT group was given HILT with analgesic dosage 10 J/cm2 and biostimulation dosage 120 J/cm2. The LLLT group was given LLLT with dosage 6 J/cm2. All treatments were given for ten sessions in 2 weeks. Combined sensory index (CSI), sensory nerve conduction velocity (SNCV), and distal motoric latency (DML) were recorded before and three days after the last treatment. The mean decrease of CSI was more significant in HILT group (-0.37±0.37 ms; p=0.03). There were no significant differences in the mean increase of SNCV (HILT = 3.16±3.15 m/s, LLLT= 2.74±1.42 m/s; p=0.73) and mean decrease in DML between two groups (HILT = - 0.20 ± 0.18 ms , LLLT = - 0.14 ± 0.21 ms; p=0.52). In conclusion, the HILT is more effective than LLLT in improving the CSI values in moderate CTS patients.
... 11 Regarding the magnitude of the laser dose given, the Arndt-Schultz Law states that small doses stimulate, medium doses inhibit, and high doses terminate. 22 The current authors suggest that, in the current study, the treatments offered were more extensive, and thus had a stunting effect. ...
Objective: Previous studies have demonstrated that laserpuncture has a positive effect on longitudinal bone growth within varying parameters. The current authors hypothesized that laserpuncture affects serum concentration of insulinlike growth factor 1 (IGF-1), a growth factor that influences growth plates, and ghrelin, a growth hormone (GH) secretagogue. The goal of this research was to investigate if laserpuncture could increase serum concentrations of IGF-1 and ghrelin in adolescent rats. Materials and Methods: This was an experimental study with a post-test only and a controlled group design. The study was performed in a laboratory on 40 male Wistar rats, age ±3 weeks and weighing >40 g. The rats were divided randomly into 2 groups, A and B, each receiving laserpuncture for 10 days and 15 days, respectively. There were 4 subgroups in each group: control (C); GV 20; ST 36; and GV 20 + ST 36. The rats were stimulated by laserpuncture with a KX Laser GX-2000B (Kangxing), a semiconductor-based low-level laser therapy (LLLT) device emitting a cold red laser (635-680 nm/5 mW) for 60 seconds (0.3 J/cm²) The length of each rat's lower limb was measured using a caliper; IGF-1 and ghrelin concentrations were assessed using enzyme-linked immunosorbent assays. Results: A marked increase in IGF-1 concentration was observed in the ST 36 and GV 20 + ST 36 subgroups after 15 days, compared to the C subgroup (P = 0.001 and P = 0.002, respectively). The GV 20 subgroup had a lower IGF-1 concentration than the C subgroup (P = 0.06) at both 10 and 15 days. Laserpuncture did not influence ghrelin concentrations significantly, compared to the C subgroups. Conclusions: Laserpuncture administered to both the ST 36 and GV 20 + ST 36 subgroups with a power density of 0.3 J/cm² increased serum concentrations of IGF-1 in adolescent rats.
... Low Level Laser Irradiation (LLLI) or in medical term, Low Level Laser Therapy (LLLT) is irradiated with lowpowered laser that induce therapeutic changes [1]. This mean, it does not cause any change to the biological tissue except for the effect of photochemistry. ...
... The propagation of laser in tissues is a question of growing importance in many diagnostic and therapeutic application in today's photo-medicine [5]. In the first Law of Photobiology, it stated that in order to have any effect by low power light beam, photons must absorbed by electronic bands of molecular photoreceptors or chromophores [1]. Chromophores in blood is haemoglobin which is the main absorber of visible light in blood [5]. ...
This study was conducted to investigate the effect of Low Level Laser Irradiation of ATP content on anaemic human blood cells. This work measured the optical density of RBCs to study the effect of ATP level after irradiated by the laser. The Low Level Laser used in this work is 589nm laser. Two aliquots of normal and anaemic blood sample were prepared, one as the control (un-irradiated) while the other one was irradiated with the laser at 20 mW, 40 mW and 60 mW which each have been irradiated at 15 minutes, 30 minutes and 45 minutes of exposure time. The ATP level of RBCs of normal and anaemic blood sample were measured by using CellTiter-Glo Luminescent cell Viability Assay Kit which generates a glow signal produced by luciferase reaction. Optical Density, as the unit to measured ATP level was tested using ELISA reader. The result shows that the ATP level is increased for anaemic RBCs after the irradiation for 20 mW, 40 mW and 60 mW, each at 15 minutes, 30 minutes and 45 minutes of exposure time. The cell viability for the anaemic also shows an increase compared to the un-irradiated one. The paired T-test is used to analyse each power irradiation and the effect of irradiation on RBCs were significant over different exposure time which all p-value is p = 0.000.
... Existen diversas técnicas de hipertermia donde se usa una fuente de calor diferente en cada una, sin embargo, en hipertermia óptica la luz láser es la fuente utilizada principalmente. Esta luz láser es altamente confiable en este tipo de hipertermia debido a sus características de monocromaticidad, coherencia y colimación [10], utilizada en una región de infrarrojo cercano (o NIR) debido a la profunda penetración del tejido biológico por su muy baja absorción por molécula de agua y hemoglobina en esta región espectral [11]. Entre otras técnicas de hipertermia óptica, se encuentra la terapia fotodinámica [3], o la fotoquimioterapia, basada en el empleo de fotosensibilizadores químicos; el uso de nanotubos de carbono [12] también es efectivo, especialmente por sus características de absorción de la luz visible, la luz láser NIR y la irradiación de radiofrecuencia y su transformación en calor. ...
After the fusion of nanotechnology with medicine and bioengineering, fields of research
in nanomedicine and nanobioengineering were created, which broadened the
perspective of medical research and emerging new frontiers. These investigations have
allowed new methods of approach to find solutions to long-standing human biological
problems and the development and administration of therapeutic or pharmacological
diagnoses. To achieve this, nanoparticles have been developed, which are
miniaturized agents, which have given way to nanomedicine. The gold nanoparticles
used in this study are nanorods (GNR) coated with G protein, a common receptor for
mechanically anchoring antibodies. In this research hyperthermia plays a role of
greatest importance which refers to the application of heat to destroy malignant cells by
induction of apoptosis through the denaturation of proteins and the rupture of cell
membranes. The application of gold nanoparticles generated by optical hyperthermia
improve in-vitro therapy, and considerable advances were made in-vivo for animal
models. In magnetic hyperthermia, the conversion of electromagnetic energy into heat
generated by SPIONs subjected to alternating magnetic fields (HAC) can be used to
cause the death of tumour cells. Recent studies have shown that the magnetic
response, and therefore the heating efficiency of SPIONs, are significantly reduced
when these nanoparticles are placed in viscous carrier liquids and within living cells or
biological tissues. The higher viscosity of the biological environment and the spatial
distribution or agglomeration of nanoparticles within the intracellular organelles strongly
influence the efficacy of SPIONs to increase the temperature of the surrounding
medium. These factors that arise from the nanobio-interaction make the heating
efficiency in in-vivo applications less efficient and predictable than in ideal ferrofluids.
Considerable advances were made in both techniques, in optical hyperthermia it was
included until obtaining improvements in the introduction of dispersant material and
biocompatible light such as Silica. The results suggested a considerable improvement
in all the variables involved in the system such as irradiated power, time of exposure to
the laser, concentration of gold nanoparticles (nanorods) and maintaining the mortality
rate in cancer cells (CT2A) against cell lines considered healthy (MC3T3). In the case
of magnetic hyperthermia, an electronic system was designed and built to generate
excitatory waveforms different from conventional ones (sinusoidal), tolerance tests
were carried out on the nanoparticles that will be used in the system. Also, it was
demonstrated the existing physical phenomenon when the SPIONs are phagocytized
by the cells, applying an intracellular interior emulator using biocompatible materials
such as worm silk fibroine.
... Noninvasive and painless nature of the laser is useful to provide comfort and relieve the fear of children. Although the use of low-power, laserpuncture has the same principles of traditional acupuncture and capable of the same biological effects with acupuncture needles [12,13,14,15,16,17]. If acupoint is stimulated by laser with particular dose, it will effect on the body system. ...
... If acupoint is stimulated by laser with particular dose, it will effect on the body system. The impulse in the form of laser is delivered by the nervous system to higher center and will stimulate hormonal releasing from hypothalamus, and then stimulate hypophysis, and it eventually will release growth factor which influences growth [16,17,18]. ...
Epiphyseal plate was used for determining longitudinal bone growth. Laserpuncture was believed to stimulate height growth. We used 40 male Wistar rats which aged three weeks old and weighed more than 40 g as subjects. They randomly divided into group A or B and each group evenly divided into four subgroups which were a negative control and others applied with laser on GV20, ST 36 or combination of GV 20+ST 36 respectively. These acupoints were then stimulated using the laser. After treatment, mice were sacrificed, then tibias were taken for histology preparation processes. By light microscope, epiphyseal plate (EP) height (µm) and chondrocytes hypertrophy (CH) height were measured at six equidistant points, and the values were averaged to obtain a final result for each section. Collected data were analyzed using ANOVA test, and the significant value was set up p< 0.05. The mean of EC and CH were lower than control, but mean of ratio EP/CH were higher than control. However, ANOVA showed that there did not differ significantly (p=0.36).
