Photobiomodulation or low-level light therapy has been shown to attenuate both acute and chronic pain, but the mechanism of action is not well understood. In most cases, the light is applied to the painful area, but in the present study we applied light to the head. We found that transcranial laser therapy (TLT) applied to mouse head with specific parameters (810 nm laser, 300 mW/cm2, 7.2 or 36 J/cm2) decreased the reaction to pain in the foot evoked either by pressure (von Frey filaments), cold, or inflammation (formalin injection) or in the tail (evoked by heat). The pain threshold increasing is maximum around 2 h after TLT, remains up to 6 h, and is finished 24 h after TLT. The mechanisms were investigated by quantification of adenosine triphosphate (ATP), immunofluorescence, and hematoxylin and eosin (H&E) staining of brain tissues. TLT increased ATP and prostatic acid phosphatase (an endogenous analgesic) and reduced the amount of glutamate receptor (mediating a neurotransmitter responsible for conducting nociceptive information). There was no change in the concentration of tubulin, a constituent of the cytoskeleton, and the H&E staining revealed no tissue damage.
Low level laser (light) therapy (LLLT) also known as photobiomodulation (PBM) therapy has been practiced for almost
fifty years, and hundreds of positive clinical trials and thousands of laboratory studies have been published. Despite these
impressive accomplishments LLLT has still not reached the stage of acceptance by mainstream medicine. The reasons
for this were discussed at a recent Optical Society of America (OSA) Incubator meeting in Washington DC in 2014.
Uncertainty about mechanisms was highlighted, and this paper will describe the current thinking. To drive LLLT
towards mainstream medicine, we need better guidelines with standardized protocols and consistent parameters. Studies
should be published in higher impact scientific and medical journals. Companies should avoid false promises and
deceptive marketing, and physicians should receive a clearly defined return on investment with insurance
reimbursement.
Background: The methods used for evaluating wound dimensions, especially the chronic ones, are invasive and inaccurate. The fringe projection technique with phase shift is a non-invasive, accurate and low-cost optical method. Objective: The aim is to validate the technique through the determination of dimensions of objects of known topography and with different geometries and colors to simulate the wounds and tones of skin color. Taking into account the influence of skin wound optical factors, the technique will be used to evaluate actual patients’ wound dimensions and to study its limitations in this application. Methods: Four sinusoidal fringe patterns, displaced ¼ of period each, were projected onto the objects surface. The object dimensions were obtained from the unwrapped phase map through the observation of the fringe deformations caused by the object topography and using phase shift analysis. An object with simple geometry was used for dimensional calibration and the topographic dimensions of the others were determined from it. After observing the compatibility with the data and validating the method, it was used for measuring the dimensions of real patients’ wounds. Results and Conclusions: The discrepancies between actual topography and dimensions determined with Fringe Projection Technique and for the known object were lower than 0.50 cm. The method was successful in obtaining the topography of real patient’s wounds. Objects and wounds with sharp topographies or causing shadow or reflection are difficult to be evaluated with this technique.
Over the last few years, low-level light therapy (LLLT) has shown an incredible suitability for a wide range of applications for central nervous system (CNS) related diseases. In this therapeutic modality light dosimetry is extremely critical so the study of light propagation through the CNS organs is of great importance. To better understand how light intensity is delivered to the most relevant neural sites we evaluated optical transmission through slices of rat brain point by point. We experimented red (λ = 660 nm) and near infrared (λ = 808 nm) diode laser light analyzing the light penetration and distribution in the whole brain. A fresh Wistar rat (Rattus novergicus) brain was cut in sagittal slices and illuminated with a broad light beam. A high-resolution digital camera was employed to acquire data of transmitted light. Spatial profiles of the light transmitted through the sample were obtained from the images. Peaks and valleys in the profiles show sites where light was less or more attenuated. The peak intensities provide information about total attenuation and the peak widths are correlated to the scattering coefficient at that individual portion of the sample. The outcomes of this study provide remarkable information for LLLT dose-dependent studies involving CNS and highlight the importance of LLLT dosimetry in CNS organs for large range of applications in animal and human diseases.
Due to the great number of applications of Low-Level-Laser-Therapy (LLLT) in Central Nervous System
(CNS), the study of light penetration through skull and distribution in the brain becomes extremely
important. The aim is to analyze the possibility of precise illumination of deep regions of the rat brain,
measure the penetration and distribution of red (λ = 660 nm) and Near Infra-Red (NIR) (λ = 808 nm)
diode laser light and compare optical properties of brain structures. The head of the animal (Rattus
Novergicus) was epilated and divided by a sagittal cut, 2.3 mm away from mid plane. This section of rat's
head was illuminated with red and NIR lasers in points above three anatomical structures: hippocampus,
cerebellum and frontal cortex. A high resolution camera, perpendicularly positioned, was used to obtain
images of the brain structures. Profiles of scattered intensities in the laser direction were obtained from
the images. There is a peak in the scattered light profile corresponding to the skin layer. The bone layer
gives rise to a valley in the profile indicating low scattering coefficient, or frontal scattering. Another
peak in the region related to the brain is an indication of high scattering coefficient (μs) for this tissue.
This work corroborates the use of transcranial LLLT in studies with rats which are subjected to models of
CNS diseases. The outcomes of this study point to the possibility of transcranial LLLT in humans for a
large number of diseases.
Due to the great number of new clinical applications of Low-Level-Laser-Therapy (LLLT), the development of precise,
stable and low cost solid phantoms of skin, fat, muscle and bone becomes extremely important. The aim is to find the
best combination of matrix, absorber and scatterers, which simulate skin, fat, muscle and bone tissues to build LLLT
phantoms. Eight cylindrical phantoms simulating various human fingers were constructed and tested. Matrixes of
polyester resins and paraffin were used with various concentrations of dyes and scatterers (Al2O3 nanoparticles) to adjust
the optical parameters. A CCD camera was used to obtain transmission and scattering images of the phantoms, and of
swine tissues and volunteer's fingers illuminated by lasers (diode 635 and 820 nm, and HeNe, 633 nm). The light fluence
transmitted through the sample form Gaussian shaped profiles. Light scattered at 90 degrees shows an intensity profile
with a steep growth followed by an exponential attenuation. The comparison of these two kinds of profiles for phantoms
and swine tissue was used to evaluate the concentrations that better simulate different kinds of tissues. The outcomes of
this study point to a reliable tool to aid clinicians with LLLT dosimetry.
MCML1.2.2-2000 code was used to simulate light distribution in LipovenosR 10% (Lp) layers with various
thicknesses illuminated by red laser. Light fluence distribution at the layer bottom and fluence profile along a
plane distant 5.5 mm from the laser beam were calculated. The results show that the light transmitted to the
bottom of the sample has a Gaussian distribution with widths that increase linearly with the thickness. Also,
the maximum light intensity and the total fluence transmitted across the sample have exponential decay
behavior with thickness. An experiment has been carried out, acquiring, with a CCD camera, pictures of light
transmitted and scattered at 90° from a cuvette containing different quantities of Lp, illuminated from the top
with He-Ne laser. The experimental results show that the maximum intensity of transmitted light has an
asymptotic exponential behavior with the sample thickness, very similar to the simulation. Gaussian curves
fitted to the experimental results have widths similar to the simulated ones. The simulated light profile at
5.5 mm from the incidence plane is very similar to the variation of scattered light intensity with depth. We
conclude that images of illuminated tissue combined with MCS can contribute with evaluation of light
distribution inside tissue.
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