Phototherapies have been increasingly used in several applications such as the control of pain and inflammatory processes, photodynamic therapy, and even aesthetics uses. After many decades, the dosimetry for those techniques remains challenging. One of the key issues is the lack of homogeneity obtained for tissue illumination, which may limit adequate treatment. Especially concerning lesions, the surface tissue is usually irregular, and the light does not couple to the tissue efficiently to promote an effective treatment. A series of experiments have been performed using optical phantoms, in which coupling was improved by introducing a gel with a low concentration of scattering agents between the fiber and the phantom as an attempt to improve the homogeneity of light distribution within the phantoms. The effects promoted by roughness on phantom tissue surfaces are considerably attenuated when the coupling gel was introduced, resulting in a more uniform illumination pattern that may be used to promote better phototherapy treatments outcome.
Photodynamic therapy is a therapeutic modality for cancer treatment based on the interaction of light with a sensitizer agent and molecular oxygen present into the target cells. The aim of this study is the evaluation of photodynamic therapy using pulsed light source in the femtosecond regime through necrosis induced in healthy rat liver. The induced necrosis profile with CW laser and pulsed laser were evaluated in animal model, which received Photodithazine (chlorine e6 derivative). The light sources used in these studies were a 660 nm CW diode laser and a Ti:Sapphire Regenerative Amplifier laser (1 kHz repetition rate and 100 fs pulse width) associated with an optical parametric amplifier (OPA) to convert to 660 nm. The results were compared with a previous study when was used a hematoporphyrin derivative (Photogem) as a sensitizer. The induced necrosis with Photogen was greater with pulsed laser (2.0 ± 0.2 mm) in comparison with CW laser (1.0 ± 0.2 mm), while in Photodithazine the induced necrosis with was greater with CW laser (2.9 ± 0.2 mm) comparing the pulsed laser (2.0 ± 0.2 mm). These results indicate dependence of PDT mechanisms with photosensitizer and the light regime applied.
Photodynamic therapy (PDT) is a treatment modality that can be indicated for several cancer types and pre-cancer lesions. One of the main applications of PDT is the treatment of superficial skin lesions such as basal cell carcinoma, Bowen’s disease and actinic keratosis. Three elements are necessary in PDT, a photosensitizer (PS); light at specific wavelength to be absorbed by the PS, and molecular oxygen. A typical PS used for skin lesion is protoporphyrin IX (PpIX), which is an intrinsic PS; its production is stimulated by a pro-drug, such as 5-aminolevulinic acid (ALA). Before starting a treatment, it is very important to follow up the PpIX production (to ensure that enough PS was produced prior to a PDT application) and, during a PDT session, to monitor its photodegradation (as it is evidence of the photodynamic effect taking place). The aim of this paper is to present a unique device, LINCE (MMOptics - São Carlos, Brazil), that brings together two probes that can, respectively, allow for fluorescence imaging and work as a light source for PDT treatment. The fluorescence probe of the system is optically based on 400 nm LED (light emitting diodes) arrays that allow observing the fluorescence emission over 450 nm. The PDT illumination probe options are constituted of 630 nm LED arrays for small areas and, for large areas, of both 630 nm and 450 nm LED arrays. Joining both functions at the same device makes PDT treatment simpler, properly monitorable and, hence, more clinically feasible. LINCE has been used in almost 1000 PDT treatments of superficial skin lesions in Brazil, with 88.4% of clearance of superficial BCC.
Considering several clinical situations, low intensity laser therapy has been widely applied in pain relief or analgesia mechanism. With the advent of new LED-based (light emitting diode) light sources, the need of further clinical experiments aiming to compare the effectiveness among them is paramount. The LED system therapeutic use can be denominated as LEDT - Light Emitting Diode Therapy. This study proposed two clinical evaluations of pain relief effect: to dentin hypersensitivity and to cervicogenic headache using different sources of lasers (low and high intensity) and light emitting diodes (LEDs), one emitting at the spectral band of red (630+/- 5nm) and the other one at infrared band (880+/- 5nm). Two different clinical studies were performed and presented interesting results. Considering dentin hypersensitivity, red and infrared led were so effective than the control group (high intensity laser system); by the other side, considering cervicogenic headache, control group (infrared laser) was the best treatment in comparison to red and infrared led system.
Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.
Infectious pneumonia is a major cause of morbidity and mortality, despite advances in diagnostics and therapeutics in
pulmonary infections. One of the major difficulties associated with the infection comes from the high rate of antibiotic
resistant microorganisms, claiming for the use of alternative techniques with high efficiency and low cost. The
photodynamic inactivation (PDI) is emerging as one of the great possibilities in this area, once its action is oxidative, not
allowing microorganism develops resistance against the treatment. PDI for decontamination pulmonary has potential for
treatment or creating better conditions for the action of antibiotics. In this study, we are developing a device to
implement PDI for the treatment of lung diseases with extracorporeal illumination. To validate our theory, we performed
measurements in liquid phantom to simulate light penetration in biological tissues at various fluency rates, the
temperature was monitored in a body of hairless mice and the measurements of light transmittance in this same animal
model. A diode laser emitting at 810 nm in continuous mode was used. Our results show 70% of leakage at 0.5 mm of
thickness in phantom model. The mouse body temperature variation was 5.4 °C and was observed light transmittance
through its chest. These results are suggesting the possible application of the extracorporeal illumination using infrared
light source. Based on these findings, further studies about photodynamic inactivation will be performed in animal model
using indocyanine green and bacteriochlorin as photosensitizers. The pulmonary infection will be induced with
Streptococcus pneumoniae and Klebsiella pneumoniae.
The purpose of this study is the assembly and characterization of a custom-made non-linear microscope. The microscope allows the adjustment for in vitro, in vivo and ex vivo imaging of biological samples. Two galvanometer mirrors conjugated by two spherical mirrors are used for the lateral scan and for the axial scan a piezoeletric stage is utilized. The excitation is done using a tunable femtosecond Ti: Sapphire laser. The light is focused in tissue by an objective lens 20X, water immersion, numerical aperture of 1.0, and working distance of 2.0 mm. The detection system is composed by a cut off filter that eliminates laser light back reflections and diverse dichroic filters can be chosen to split the emitted signal for the two photomultiplier detector. The calibration and resolution of the microscope was done using a stage micrometer with 10 μm divisions and fluorescent particle slide, respectively. Fluorescence and second harmonic generation images were performed using epithelial and hepatic tissue, the images have a sub-cellular spatial resolution. Further characterization and differentiation of tissue layers can be obtained by performing axial scanning. By means of the microscope it is possible to have a three dimensional reconstruction of tissues with sub-cellular resolution.
One of the limitations of PDT in the treatment of bulk tumors is the light penetration in biological tissues at the red
spectrum. PDT illumination at short pulsed regime may present a higher light penetration compared to the CW regime,
and potentially a higher volume of induced necrosis. The major goal of this study was an in vitro and in vivo evaluation
of PDT response after illumination using a 630 nm femtosecond laser. Photogem in distilled water solution was
illuminated either with CW or femtosecond laser under the same fluence and fluence rate parameters. Wistar rats
weighting between 280 and 300 g were intravenously photosensitized with Photogem. Thirty minutes after drug
injection, the normal liver was irradiated either with the CW or the femtosecond laser (fluence: 150 J/cm2). The in vitro
results showed that, under the same conditions, the degradation rate evaluated via fluorescence spectroscopy was higher
under femtosecond laser irradiation. Histological analysis of the induced necrosis showed that there was a significant
higher depth of necrosis when the femtosecond laser was used. Based on these results, femtosecond lasers seem to be an
alternative in PDT applications, improving results for the treatment of lesions for which a larger light penetration is
required.
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