Dye Laser Radiation Research Articles

Carbon monoxide combined with artificial blood cells acts as an antioxidant for tissues thermally-damaged by dye laser irradiation

Artificial red blood cells [i.e., hemoglobin vesicles (HbVs)] can be used as photosensitizers in pulsed-dye laser (PDL) treatment for port wine stains in animal models. Small HbVs are distributed in the vicinity of the endothelial cells of the blood vessels. In our previous in vivo experiments, both HbVs and red blood cells absorbed photons of the laser and generated heat, contributing to removal of very small blood vessels and large deeper subcutaneous blood vessels with PDL irradiation. Herein, we tested carbon monoxide-bound HbVs (CO-HbVs) that would produce heat energy while releasing CO in vessels after dye laser irradiation in a rabbit auricle model. We conducted this experiment to confirm secondary progression of thermal injury being reduced with the antioxidative property of CO. We histopathologically evaluated the damages to the large vessels and surrounding dermal tissue following PDL irradiation alone or subsequent to the intravenous injection of the qualified HbVs. The soft tissue damages were graded on a five-point scale and compared statistically. Intravenous CO-HbVs significantly reduced damage to the surrounding tissue after subsequent PDL irradiation; however, the degree of damage to the larger vessel wall resulted in a variety of changes, including a slight increase in our histopathological grades. This beneficial effect in dye laser treatment for port wine stains may be the result of the antioxidative property of CO against free radicals in the zone of stasis that may still be theoretically viable in burns. This effect of CO protecting tissues from thermal damage is consistent with previous reports of CO as a reducing agent. If the reducing agent can be delivered directly to the affected area immediately after the burn injury, even in a small amount, the complex inflammatory cascade may be reduced and unnecessary inflammation after laser treatment that lowers the patient’s quality of life can be avoided.

Topical metformin suppresses angiogenesis pathways induced by pulsed dye laser irradiation in animal models.

Pulsed dye laser (PDL) is the first-line treatment for port-wine stain (PWS). However, only a small portion of the lesions could be completely cleared by PDL treatment, which might be related to the regeneration and revascularization of the vascular structures after laser irradiation. Recently, it is believed that the suppression of regeneration and revascularization of photocoagulated blood vessels can achieve a better therapeutic outcome. We use rabbit ear and SD rat as the animal models to investigate whether PDL-induced angiogenesis can be suppressed by topical metformin. Our results showed that topical application of metformin can effectively suppress the PDL-induced early stage of angiogenesis via inhibition of the AKT/mTOR/P70S6K pathway in animal models.

Efficient second-harmonic and terahertz generation from single BiB3O6crystal using nanosecond and femtosecond lasers.

The paper reports the efficient UV and terahertz generation from a 1.29 mm thick and Type I, θ=28.9∘ cut BiB3O6 (bismuth triborate, BIBO) crystal using femtosecond and nanoseconds laser pulses. We have employed 800 nm wavelength pulses of 50 and 140 fs obtained from a Ti:sapphire laser amplifier and oscillators at 1 kHz and 80 MHz repetition rates, respectively. The conversion efficiency of second-harmonic generation (SHG) was ∼50% while that obtained for terahertz (THz) generations was of the order of 1.85×10-5%. In addition, LDS-698 dye laser radiation tunable between 650-700 nm was also used as a source for SHG between the 325-350 nm range. The dye laser was pumped by SHG (532 nm) radiation from an electro-optically Q-switched Nd:YAG laser having a pulse repetition rate of 10 Hz and a pulse width of 10 ns. A conversion efficiency of 4.01% was obtained for generation of UV at 343.5 nm. Finally, we have measured the transmission, refractive index, absorbance, and conductivity properties of BIBO crystal in the THz domain. We also ascertained the coherence length, relative permittivity and reflectivity of the crystal.

Photothermal treatment of port-wine stains using erythrocyte-derived particles doped with indocyanine green: a theoretical study.

.Pulsed dye laser irradiation in the wavelength range of 585 to 600 nm is currently the gold standard for treatment of port-wine stains (PWSs). However, this treatment method is often ineffective for deeply seated blood vessels and in individuals with moderate to heavy pigmentation. Use of optical particles doped with the FDA-approved near-infrared (NIR) absorber, indocyanine green (ICG), can potentially provide an effective method to overcome these limitations. Herein, we theoretically investigate the effectiveness of particles derived from erythrocytes, which contain ICG, in mediating photothermal destruction of PWS blood vessels. We refer to these particles as NIR erythrocyte-derived transducers (NETs). Our theoretical model consists of a Monte Carlo algorithm to estimate the volumetric energy deposition, a finite elements approach to solve the heat diffusion equation, and a damage integral based on an Arrhenius relationship to quantify tissue damage. The model geometries include simulated PWS blood vessels as well as actual human PWS blood vessels plexus obtained by the optical coherence tomography. Our simulation results indicate that blood vessels containing micron- or nano-sized NETs and irradiated at 755 nm have higher levels of photothermal damage as compared to blood vessels without NETs irradiated at 585 nm. Blood vessels containing micron-sized NETs also showed higher photothermal damage than blood vessels containing nano-sized NETs. The theoretical model presented can be used in guiding the fabrication of NETs with patient-specific optical properties to allow for personalized treatment based on the depth and size of blood vessels as well as the pigmentation of the individual’s skin.

Trace Determination of Germanium by Continuous Flow Hydride Generation Laser-Induced Fluorescence Spectrometry

A continuous flow hydride generation laser-induced fluorescence (HG-LIF) spectrometry technique has been investigated for performing trace determination of germanium (Ge). Hydride generation of Ge is performed using reagent concentrations of 2 M H3PO4 and 0.5% NaBH4 and fluorescence detection is performed using tunable dye laser radiation at 253.323 nm for Ge excitation with fluorescence measured at 303.907 nm. The HG-LIF approach provides a linear response for Ge in the concentration range from 1.0 to 50 ng mL−1 and a limit of detection of 0.1 ng mL−1. Replicate measurements at 10 ng mL−1 have a relative standard deviation of 0.1% (n = 8). Measurements of Ge in different sample matrices have demonstrated the effectiveness of thiourea and ascorbic acid as masking agents that compensate for samples containing interfering ions. The determinations of the Ge content in reference water samples, fly ash samples, and supplement capsules demonstrate that the HG-LIF approach has feasibility for measuring Ge in different sample matrices at environmentally relevant concentrations.

Comparative numerical analysis and optimization of blood vessels heated using various lasers

Numerical simulation was introduced to study selective vessel heating using diode laser, Nd:YAG laser, copper vapor laser and pulsed dye laser radiation. The vessels’ location depth and size were determined, which could ensure selective heating of the vessels to the coagulation temperature. These results are in good agreement with clinical findings, and the validity of our model is confirmed.

Intravenous injection of artificial red cells and subsequent dye laser irradiation causes deep vessel impairment in an animal model of port-wine stain.

Our previous study proposed using artificial blood cells (hemoglobin vesicles, Hb-Vs) as photosensitizers in dye laser treatment for port-wine stains (PWSs). Dye laser photons are absorbed by red blood cells (RBCs) and hemoglobin (Hb) mixture, which potentially produce more heat and photocoagulation and effectively destroy endothelial cells. Hb-Vs combination therapy will improve clinical outcomes of dye laser treatment for PWSs because very small vessels do not contain sufficient RBCs and they are poor absorbers/heaters of lasers. In the present study, we analyzed the relationship between vessel depth from the skin surface and vessel distraction through dye laser irradiation following intravenous Hb-Vs injection using a chicken wattle model. Hb-Vs were administered and chicken wattles underwent high-energy irradiation at energy higher than in the previous experiments. Hb-Vs location in the vessel lumen was identified to explain its photosensitizer effect using human Hb immunostaining of the irradiated wattles. Laser irradiation with Hb-Vs can effectively destroy deep vessels in animal models. Hb-Vs tend to flow in the marginal zone of both small and large vessels. Increasing laser power combined with Hb-Vs injection contributed for deep vessel impairment because of the synergetic effect of both methods. Newly added Hb tended to flow near the target endothelial cells of the laser treatment. In Hb-Vs and RBC mixture, heat transfer to endothelial cells from absorbers/heater may increase. Hb-Vs function as photosensitizers to destroy deep vessels within a restricted distance that the photon can reach.

Development of a see-through hollow cathode discharge lamp for (Li/Ne) optogalvanic studies.

Development of a demountable and see-through hollow cathode (HC) discharge lamp suitable for optogalvanic (OG) spectroscopy is described. The design of the HC lamp is simple, compact, and inexpensive. Lithium, investigated rarely by the OG method, is selected for cathode material as its isotopes are important for nuclear industry. The HC lamp is characterized electrically and optically for discharge oscillations free OG effect. Strong OG signals of lithium as well as neon (as buffer gas) are produced precisely upon copper vapor laser pumped tunable dye laser irradiation. The HC lamp is capable of generating a clean OG resonance spectrum in the available dye laser wavelength scanning range (627.5-676 nm) obtained with 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dye. About 28 resonant OG lines are explicitly observed. Majority of them have been identified using j-l coupling scheme and assigned to the well-known neon transitions. One line that corresponds to wavelength near about 670.80 nm is assigned to lithium and resolved for its fine (2S1/2 → 2P1/2, 3/2) transitions. These OG transitions allow 0.33 cm-1 accuracy and can be used to supplement the OG transition data available from other sources to calibrate the wavelength of a scanning dye laser with precision at atomic levels.

Artificial Red Blood Cells as Potential Photosensitizers in Dye Laser Treatment Against Port-Wine Stains.

We suggest a novel method that uses artificial blood cells (hemoglobin vesicles, Hb-Vs) as photosensitizers in dye laser treatment (at 595-nm wavelength) for port-wine stains (i.e., capillary malformations presenting as red birthmarks) based on the results of animal experiments. As compared with human red blood cells, Hb-Vs have the same absorbance of 595 nm wavelength light and produce the same level of heat following dye laser irradiation. Small sized Hb-Vs (250 nm) distribute in the plasma phase in blood and tend to flow in the marginal zone of microvessels. Intravenous injections of Hb-Vs caused the dilatation of microvessels, and dye laser treatment with Hb-Vs destroyed the vessel wall effectively. Following the intravenous injection of Hb-Vs, the microvessels contained more Hb that absorbed laser photons and produced heat. This extra Hb tended to flow near the endothelial cells, which were the target of the laser treatment. These attributes of Hb-Vs will potentially contribute to enhancing the efficacy of dye laser treatment for port-wine stains. Hemoglobin is a type of porphyrin. Thus, our proposed treatment may have aspects of photodynamic therapy using porphyrin that leads to a cytotoxicity effect by active oxygen.

Photosensitizer Effects of Artificial Red Cells on Dye Laser Irradiation in an Animal Model Assuming Port-Wine Stain Treatment.

The complete removal of port-wine stains has remained challenging. Based on the principle of treating port-wine stains with a dye laser, intravenous injection of artificial red cells (hemoglobin vesicles) immediately before laser treatment might improve the clinical outcome of the therapy. The hemoglobin vesicle injection increases the hemoglobin concentration in microvessels. Photons of dye laser are absorbed by the mixture of red blood cells and this newly added hemoglobin, potentially producing more heat and photocoagulation and, ultimately, necrosis of the endothelial cells effectively. To confirm the performance of hemoglobin vesicles as a photosensitizer, the authors compared the absorbance of hemoglobin vesicles and human blood against 595-nm wavelength and the temperature increases that occur following dye laser irradiation. Furthermore, the authors investigated the microvessel transformation induced by the hemoglobin vesicle intravenous injection. Finally, the authors investigated the effect of the hemoglobin vesicle on the vascular destruction of dye laser irradiation with chicken wattle. Results show that hemoglobin vesicles have the same absorbance as that of human blood. They produce the same level of heat as human blood after laser irradiation. The hemoglobin vesicle intravenous injection caused dilatation of microvessels in animal models. The dye laser with hemoglobin vesicle can destroy the vessel wall effectively in animal models. Hemoglobin vesicles can function as photosensitizers to destroy the vessel wall. A possible mechanism of pulsed dye laser-resistant port-wine stains is that overly small vessels do not contain sufficient red blood cells. They are therefore poor absorbers/heaters for these lasers. Hemoglobin vesicle combination therapy will improve clinical outcomes of dye laser treatment against such lesions only.

Clinical comparison between photodynamic therapy and pulsed dye laser for the treatment of port wine stains

Objective To compare the clinical efficacy and adverse effects of photodynamic therapy(PDT)versus pulsed dye laser(PDL)for the treatment of port wine stains(PWS). Methods Forty-five patients with PWS were enrolled in this study. The PWS lesions in each patient were randomly divided into PDT and PDL areas. Hematoporphyrin monomethyl ether of 5 mg/kg was injected intravenously into the PDT area protected from light, followed by 20-minute irradiation with a 532-nm, solid-state, continuous-wave laser(power density: 80-100 mw/cm2; spot diameter: 7 cm)10 minutes later. The PDL area was treated with a single session of 595-nm pulsed dye laser radiation(spot diameter: 7 mm; pulse width: 10 ms; energy density: 10-12 J/cm2). The interval between PDT and PDL treatment was no shorter than two months. Follow up visits were scheduled on day 4 and week 8 after each treatment. Adverse reactions were recorded, and photographs were taken before and 8 weeks after the treatment for evaluation of lesion regression. Results In the case of PDT area, 10 cases(22.22%)were nearly cured, 22(48.89%)achieved marked improvement, 9(20.00%)improvement, 4(8.89%)no improvement. As far as the PDL area is concerned, 6 cases(13.33%)were nearly cured, 16(35.56%)achieved marked improvement, 18(40.00%)improvement, and 5(11.11%)no improvement. The response rate was significantly higher in the PDT area than in the PDL area(Z = 2.48, P 0.05). Conclusion For the treatment of PWS, both PDT and PDL are effective and safe, and single-session PDT appears to be superior to single-session PDL. Key words: Port-wine stain; Phototherapy; Hematoporphyrin photoradiation

The effect of 595 nm pulsed dye laser on connective tissue growth factor (CTGF) expression in cultured keloid fibroblasts.

To investigate the effect of pulsed dye laser (PDL 595 nm) on the proliferation and expression of connective tissue growth factor (CTGF) in cultured keloid fibroblasts. Cultured keloid fibroblasts were exposed to pulsed dye laser irradiation at fluences of 6, 8, and 10 J/cm(2) , with pulse durations of 1.5, 3, and 10 ms. The viability of keloid fibroblasts was measured with CCK-8 at 72, 24, and 12 hours prior to irradiation. Subsequently, viability was measured at 12, 24, and 72 hours post-irradiation. Additionally, the fibroblast cell cycle and apoptosis rate were measured by flow cytometry. Finally, keloid fibroblasts underwent real-time polymerase chain reaction (PCR) and Western blot to investigate the CTGF mRNA and protein expression after PDL irradiation. The untreated cultured keloid fibroblasts served as controls. The proliferation of keloid fibroblasts was significantly inhibited after PDL irradiation. Both CTGF mRNA and protein expression were significantly down-regulated in 1.5, 3, and 10 ms pulse duration groups, in a dose dependent manner (P < 0.05). However, there was no statistically significant difference between groups of different pulse duration in 6, 8, and 10 J/cm(2) fluence ranges (P > 0.05). Within certain fluence ranges, pulsed dye laser can effectively suppress the growth of keloids and significantly down-regulate CTGF mRNA and CTGF expression.

THE MECHANISM OF DOUBLY CHARGED IONS FORMATION UPON MULTIPHOTON IONIZATION OF BARIUM ATOMS BY LASER RADIATION OF 16800-18700 сm&lt;sub&gt;-1&lt;/sub&gt; SPECTRAL RANGE

The process of formation of doubly charged ions upon multiphoton ionization of barium atoms by linearly and circularly polarized radiation of dye lasers is studied in the frequency range from 16 800 to 18 700 cm-1. A large number of resonance maxima in the yield of Ba+ and Ba2+ ions were observed upon tuning the radiation frequency. It is unambiguously proved that most resonance maxima in the yield of Ba2+ ions are associated with the resonance transitions in the spectrum of Ba+ ions. This fact confirms the cascade mechanism of formation of Ba2+ ions in the frequency range of localization of these maxima. Keywords: multiphoton ionization, two-charged ions, cascade mechanism, barium atom, resonant process.

Broadband picosecond radiation source based on noncollinear optical parametric amplifier

Amplification of broadband radiation of modeless dye laser by a noncollinear optical parametric amplifier based on a KTP crystal has been implemented upon pumping by second-harmonic pulses of a Nd : YAG laser. Pulses with a bandwidth of , a duration of and an energy of have been obtained at the centre wavelength of .

Photodynamic therapy for esophageal cancer.

Photodynamic therapy (PDT) is a treatment that uses a photosensitizing drug that is administered to the patient, localized to a tumor, and then activated with a laser to induce a photochemical reaction to destroy the cell. PDT using porfimer sodium followed by excimer dye laser irradiation is approved as a curative treatment for superficial esophageal cancer in Japan. While endoscopic submucosal dissection (ESD) is currently more popular for esophageal cancer, there is evidence to support PDT as an alternative treatment and as a salvage treatment for local failure after chemoradiotherapy (CRT). A photosensitizing agent has also been developed that requires a shorter sun shade period after administration, and studies are currently underway to establish an esophageal cancer indication for this next-generation PDT in Japan.

Photodissociation of (SO2⋯XH) Van der Waals complexes and clusters (XH = C2H2, C2H4, C2H6) excited at 32 040–32 090 cm−1 with formation of HSO2 and X

We studied photodecomposition dynamics of (SO2⋯XH) Van der Waals' (VdW) complexes and clusters in gas phase, with X = C2H, C2H3, and C2H5. SO2 was excited by frequency-doubled radiation of a tunable dye laser and resonance-enhanced multiphoton ionization was used to detect the C2H (m/z 25), C2H3 (m/z 27), and C2H5 (m/z 29) ions by time-of-flight mass spectroscopy. Spectra obtained at higher nozzle pressures (P0 > 2.5 atm) indicate formation of clusters. Detailed studies of the VdW complex structure were carried out by analyzing the rotational structure of the respective action spectra. We also performed ab initio theoretical analysis of structures of the VdW complexes and transitional states leading to photodecomposition. We find that the structure of the transition state is significantly different as compared to the equilibrium ground-state structure of the respective complex. The photodecomposition mechanism depends on the hydrocarbon molecule bound to SO2.

Development of coherent tunable source in 2–16 μm region using nonlinear frequency mixing processes

A very convenient way to obtain widely tunable source of coherent radiation in the infrared region is through nonlinear frequency mixing processes like second harmonic generation (SHG), difference-frequency mixing (DFM) or optical parametric oscillation (OPO). Using commonly available Nd:YAG laser and its harmonic pumped dye laser radiation as parent beams, we have been able to generate coherent tunable infrared radiation (IR) in 2–16 μm region using different nonlinear crystals by DFM and OPO. We have also generated such IR source in the 4–5 μm region through SHG of CO2 laser in different infrared crystals. In the process we have characterized a large number of nonlinear crystals like different borate group of crystals, KTP, KTA, LiIO3, MgO:LiNbO3, GaSe, AgGaSe2, ZnGeP2, AgGa1−xInxSe2, HgGa2S4 etc. To improve the conversion efficiencies of such frequency conversion processes, we have developed some novel schemes, like multipass configuration (MC) and positive optical feedback (POF). The significance of the obtained results lies in the fact that to get the same conversion in SHG or DFM, one now requires fundamental input radiation with much lower intensity.

Initiation of luminol chemiluminescence by two-quantum excitation of U(IV) in aqueous solution

Results of experiments on initiation of luminol chemiluminescence by multiquantum excitation of U(IV) in aqueous solution by dye laser radiation in the visible range are reported.

Topical application of 5-aminolevulinic acid followed by 595-nm pulsed dye laser irradiation for the treatment of recalcitrant port-wine stains: A primary study

Objective: To evaluate the effectiveness and safety of topical application of 5-aminolevulinic acid (ALA) followed by pulsed dye laser (PDL) irradiation for the treatment of recalcitrant port-wine stain (PWS). Methods: Thirty-five patients (19 females and 16 males) with recalcitrant PWS were treated with topical application of 20% ALA and then irradiated with a 595-nm PDL (energy density of 6.5–9.0 J/cm2 and pulse duration of 6 or 10 ms) at 6–8 weeks intervals. Clinical improvement of lesions was evaluated by comparing photographs of lesions at baseline and 2 months after the last treatment. Results: Topical ALA spreading followed by irradiation with a 595-nm PDL improved PWS in 21 out of 35 patients who were previously recalcitrant to PDL treatment alone. Side effects were limited to transient erythema, vesicle formation, edema and mild purpura with no obvious subsequent scarring or undesirable pigment changes. Conclusion: The topical application of ALA followed by irradiation with a 595-nm PDL is an effective and safe treatment for PWS recalcitrant to PDL therapy alone.

Photodynamic therapy as salvage treatment for local failure after chemoradiotherapy in patients with esophageal squamous cell carcinoma: A phase II study

Local failure at the primary site is a major problem after chemoradiotherapy (CRT) in patients with esophageal squamous cell carcinoma (ESCC). Salvage surgery is the only treatment option with curative intent, but it is associated with high morbidity and mortality. The aim of this study was to evaluate the efficacy and safety of salvage photodynamic therapy (PDT) after CRT. Patients with histologically proven local failure limited to the submucosal layer, and without any metastasis after definitive CRT (≥50 Gy) for ESCC were enrolled in the study. PDT began with intravenous administration of 2 mg/kg of porfimer sodium followed 48-72 hr later by excimer dye laser irradiation with a fluence of 75 J/cm2. The primary endpoint was a complete response (CR) to treatment with PDT, and the secondary endpoints were toxicity related to PDT, progression-free survival (PFS) and overall survival (OS). Twenty-five patients were enrolled in the study. A CR was attained in 19 of 25 patients treated with PDT (CR rate, 76%; 95% CI, 55-91%). One treatment-related death (4%) caused by gastrointestinal hemorrhage at the irradiated site occurred 33 days after PDT. No adverse events greater than grade 3 were related to PDT in the other patients. After a median follow-up of 48 months after PDT, the PFS and OS at 3 years were 40% (95% CI, 21-59%) and 38% (95% CI, 17-60%), respectively. PDT is a potentially curative and tolerable salvage treatment after CRT for carefully selected patients with local failure without any metastasis.