This PDF file contains the front matter associated with SPIE Proceedings Volume 8803, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

We present a time-resolved photographic analysis of the pulse-to-pulse interaction of temporally separated fs-laser pulses with various pulse overlap in water. Initially, by decreasing the temporal separation of laser pulses there is a diminishment of the laser-induced optical breakdown (LIOB) probability, caused by focusing into persisting gas bubbles at the focal volume. A LIOB at the focal spot is finally impaired by the oscillating cavitation bubble of the preceding pulse. Hence, the interaction between the laser and transparent ophthalmic tissue may be accompanied by a raised laser energy transmission and a variation in the axial cutting depth, which could be observed in case of a pulse overlap. In conclusion, our experimental results are of particular importance for the optimization of the prospective ophthalmic surgical process with future-generation fs-lasers.

Selective Retina Therapy (SRT) targets the Retinal Pigment Epithelium (RPE) without effecting neighboring layers as the photoreceptors or the choroid. SRT related RPE defects are ophthalmoscopically invisible. Owing to this invisibility and the variation of the threshold radiant exposure for RPE damage the treating physician does not know whether the treatment was successful or not. Thus measurement techniques enabling a correct dosing are a demanded element in SRT devices. The acquired signal can be used for monitoring or automatic irradiation control. Existing monitoring techniques are based on the detection of micro-bubbles. These bubbles are the origin of RPE cell damage for pulse durations in the ns and μs time regime 5μs. The detection can be performed by optical or acoustical approaches. Monitoring based on an acoustical approach has already been used to study the beneficial effects of SRT on diabetic macula edema and central serous retinopathy. We have developed a first real time feedback technique able to detect micro-bubble induced characteristics in the backscattered laser light fast enough to cease the laser irradiation within a burst. Therefore the laser energy within a burst of at most 30 pulses is increased linearly with every pulse. The laser irradiation is ceased as soon as micro-bubbles are detected. With this automatic approach it was possible to observe invisible lesions, an intact photoreceptor layer and a reconstruction of the RPE within one week.

We have determined the threshold radiant exposure for cell death in the endothelium of porcine cornea exposed to ultrashort laser pulses in the context of keratoplasty and the preparation of endothelial grafts. In this study, by progressively increasing the radiant threshold towards the higher values we have observed a decrease of living corneal endothelial cells. Further study will address the effect of dose and possible mechanism behind cell death.

In ophthalmic surgery fs laser pulses are used as a precise and safe cutting tool. At specific processing parameters, however, an interesting phenomenon of unintended periodic structures inside the tissue can be observed. In this study, a transparent polymer served as ocular phantom material for further investigations. A Femtosecond laser with MHz-repetition rate and pulse energies below 200 nJ was used. The size of the durable material change caused by applied fs-single pulses was measured in regard to the pulse energy. Furthermore, lines were cut inside the material with different laser spot distances and laser pulse energies. The creation and enhancement of unintended step-like structures could be related to a decrease of spot distance and further increase of pulse energy. Cutting planes inside the material resulted also in a formation of step like structures. For planes the step-like structures were formed with different orientation in the x-y-plane in regard to the used line distance between two applied lines. A maximum step height of 75 μm was measured using our setup. Those periodic structures are unwanted for any application in the field of laser material processing, ophthalmology or biomedical sectioning. Hence, investigations of the parameters which trigger this phenomenon are of great interest.

Biological tissues, including human skin, are complex objects for optical measurements. Because of its multi-component structure, they are characterized by a combined response to various dynamic changes, both inside and outside of the biological object. Change of glucose concentration in the blood leads to a number of processes, which affect the light scattering properties of the skin and subcutaneous layers, herewith scattering coefficient and the polarization of the scattered light vary. The possibility of non-invasive blood glucose detection by parameters of backscattered laser light was experimentally demonstrated. Degree of polarization of light scattered by human skin and model objects was registered and dependence of the polarization state of backscattered radiation on the glucose concentration in the human blood was shown. A laboratory model of a differential polarimeter, which allows registering the parameters of the polarized radiation scattered by human skin and glucose containing models was developed. Using the developed model, model and full-scale experiments were conducted. In the model experiments, the light scattered in the forward and backwards direction by the following model objects: a 20% solution of milk and a 50% solution of whole human blood was investigated. The ability of the developed sensor to noninvasively detect the concentration of glucose in the blood was demonstrated.

Genetic mutation of the β-globin gene or inheritance of this mutated gene changes the chemical composition of the oxygen-carrying hemoglobin molecule that could lead to either the heterozygote genotype, resulting in sickle cell trait (SCT), or the homozygote genotype, resulting in sickle cell anemia (SCA). These mutations could affect the reversible elastic deformations of the red blood cells (RBCs) which are vital for biological functions. We have investigated this effect by studying the differences in the deformability of RBCs from blood samples of an individual with SCT and an untreated patient with SCA along with hemoglobin quantitation of each blood sample. Infrared 1064 nm laser trap force along with drag shear force are used to induce deformation in the RBCs. Ultra2-High Performance Liquid Chromatography (UHPLC) is used for the hemoglobin quantitation.

In this work, magnetic and optical propagation in human head are modeled by FDTD and Monte Carlo methods. Both of them use a realistic high-resolution three-dimensional human head mesh. The numerical methods are applied to the analysis of magnetic and optical radiation distribution in the brain using different sources. The results show the characteristics of both types of stimulation, and highlight the spatial selectivity achieved by optical sources, which entails a high potential for illuminating specific brain regions. The presented approach can be applied for predictive purposes in magnetic stimulation techniques and in the emerging field of optical brain stimulation.

The delivery of antisense structures, like siRNA, is beneficial for new therapeutic approaches in regenerative sciences. Optical transfection techniques enable high spatial control combined with minimal invasive treatment of cells due to the use of short laser pulses. However, single cell laser transfection by a tightly focused laser beam, for example femtosecond laser transfection, has the major drawback of low throughput. Compared to this, high-throughput in laser transfection is possible by applying gold nanoparticles irradiated by a weakly focused laser beam scanning over the cell sample. Herein, we show the delivery of antisense molecules and demonstrate the minimal cytotoxicity of a method called gold nanoparticle mediated (GNOME) laser transfection. A 532 nm microchip laser in conjugation with 200 nm gold nanoparticles at a concentration of 0.5 μg/cm² is used. In addition to antisense molecules, the uptake of dextrans of several sizes is analyzed.

Near-infrared femtosecond laser pulses were applied to initiate reversible permeabilization of cell membrane and inject extrinsic substances into the target cells. Successful laser-based injection of a membrane impermeable dye, as well as plasmid DNA was demonstrated.

Begin basal cell carcinoma (BCC) is most common skin cancer over the world. There are around 20 modalities for BCC treatment. Laser surgery is uncommon option. We demonstrate our long term follow up results. Aim: To evaluate long term efficacy of a 980nm diode laser for the difficult-to-treat basal cell carcinoma. Materials and Methods: 167 patients with 173 basal cell carcinoma on the nose were treated with a 980 nm diode laser from May 1999 till May 2005 at Latvian Oncology center. All tumors were morphologically confirmed. 156 patients were followed for more than 5 years. Results: The lowest recurrence rate was observed in cases of superficial BCC, diameter<6mm; bet the highest recurrence rate was in cases of infiltrative BCC and nodular recurrent BCC. Conclusions: 980 nm diode laser is useful tool in dermatology with high long term efficacy, good acceptance by the patients and good cosmetics results.

Diagnostic potential of principal component analysis (PCA) of multi-spectral imaging data in the wavelength range 450- 950 nm for distant skin melanoma recognition is discussed. Processing of the measured clinical data by means of PCA resulted in clear separation between malignant melanomas and pigmented nevi.

A combined laser tattoo removal treatment, first the ablative fractional resurfacing (AFR) with an Er:YAG laser and then the q-switched (QSW) Nd:YAG laser treatment, was studied. Experiments show that significantly higher fluences can be used for the same tissue damage levels.

Although studies show the clinical effectiveness of low level laser therapy (LLLT) in facilitating the muscle healing process, scientific evidence is still required to prove the effectiveness of LLLT and to clarify the cellular and molecular mechanisms triggered by irradiation. Here we evaluate the effect of different LLLT doses, using continuous illumination (830 nm), in the treatment of inflammation induced in the gastrocnemius muscle of Wistar rats, through the quantification of cytokines in systemic blood and histological analysis of muscle tissue. We verified that all applied doses produce an effect on reducing the number of inflammatory cells and the concentration of pro-inflammatory TNF-α and IL-1β cytokines. The best results were obtained for 40 mW. The results may suggest a biphasic dose response curve.

To reduce unwanted collateral thermal damage to surrounding tissue and organs during laparoscopic laser dissection (cw, wavelength: 1.9μm) of porcine liver water spray was used. Size and amount of the produced water droplets of the water spray were photographed by short time imaging and analyzed by imaging software. At in vivo measurements on fresh porcine liver the depth of thermal damage was reduced by 85 % with water spray and the lateral size of thermal damage at the tissue surface could be reduced by 67%. This results show that especially for laparoscopic laser surgery water spray application might be a useful tool to avoid unwanted collateral thermal damage.

Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm² realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, the wavelength of 5.85 μm could realize the selective excavation of human carious dentin, but it was necessary to evaluate the stage of caries progression in order to control the ablation property.

We investigated the potential of a compact and high-power quantum cascade laser (QCL) in the 5.7 μm wavelength range for less-invasive laser angioplasty. Atherosclerotic plaques consist mainly of cholesteryl esters. Radiation at a wavelength of 5.75 μm is strongly absorbed in C=O stretching vibration mode of cholesteryl esters. Our previous study achieved to make cutting differences between a normal artery and an atherosclerotic lesions using nanosecond pulsed laser by difference-frequency generation (DFG laser) at the wavelength of 5.75 μm. For applying this technique to clinical treatment, a compact laser device is required. In this study, QCL irradiation effects to a porcine normal aorta were compared with DFG laser. Subsequently, QCL irradiation effects on an atherosclerotic aorta of myocardial infarction-prone Watanabe heritable hyperlipidemic rabbit (WHHLMI rabbit) and a normal rabbit aorta were observed. As a result, the QCL could make cutting differences between the rabbit atherosclerotic and normal aortas. On the other hand, the QCL induced more thermal damage to porcine normal aorta than the DFG laser at the irradiation condition of comparable ablation depths. In conclusion, the possibility of less-invasive and selective treatment of atherosclerotic plaques using the QCL in the 5.7 μm wavelength range was revealed, although improvement of QCL was required to prevent the thermal damage of a normal artery.

Aiming for laser-assisted resection of calcified aortic valve structures for Transcatheter Aortic Valve Implantation (TAVI), a Q-switched Tm:YAG laser emitting at a wavelength of 2.01 μm was used to evaluate the cutting efficiency on highly calcified human aortic leaflets in-vitro. The calcified aortic leaflets were examined regarding ablation rates and debris generation, using a pulse energy of 4.3 mJ, a pulse duration of 0.8-1 μs and a repetition rate of 1 kHz. The radiation was transmitted via a 200 μm core diameter quartz fiber. Resection was performed in a fiber-tissue contact mode on water-covered samples in a dish. The remnant particles were analyzed with respect to quantity and size by light microscopy. Additionally, soft tissue of porcine aortic vessels was examined for histologically detectable thermo-mechanical damage after continuous wave and Q-switched 2μm laser irradiation. An ablation rate of 36.7 ± 25.3 mg/min could be realised on highly calcified aortic leaflets, with 85.4% of the remnant particles being <6 μm in diameter. The maximum damaged area of the soft tissue was < 1 mm for both, cw and pulsed laser irradiation. This limits the expected collateral damage of healthy tissue during the medical procedure. Overall, the Q-switched Tm:YAG laser system showed promising results in cutting calcified aortic valves, transmitting sufficient energy through a small flexible fibre.

Both the thickness and absorption coefficient of the epidermis influence the light transmission through skin. Different skin phototypes were modeled and show a more than 50% reduction in fluence rate for the darker skin phototypes at a depth of 200 μm into the skin.

We investigated detailed extracellular photosensitization reaction effect on rat myocardial cells and the photosensitization reaction progress in a well to study a new application of photodynamic therapy for arrhythmia therapy.

Despite of the success of photodynamic therapy (PDT) in cancer treatment, the problems of low selective accumulation of a photosensitizer in a tumor and skin phototoxicity have not resolved yet. The idea of encoding of a photosensitizer in genome of cancer cells is attractive, particularly because it can provide highly selective light induced cell killing. This work is aimed at the development of new approach to PDT of cancer, namely to using genetically encoded photosensitizers. A phototoxicity of red fluorescent GFP-like protein KillerRed and FMN-binding protein miniSOG was investigated on HeLa tumor xenografts in nude mice. The tumors were generated by subcutaneous injection of HeLa cells stably expressing the phototoxic proteins. The tumors were irradiated with 594 nm or 473 nm laser at 150 mW/cm² for 20 or 30 min, repeatedly. Fluorescence intensity of the tumors was measured in vivo before and after each treatment procedure. Detailed pathomorphological analysis was performed 24 h after the therapy. On the epi-fluorescence images in vivo photobleaching of both proteins was observed indicating photodynamic reaction. Substantial pathomorphological abnormalities were found in the treated KillerRed-expressing tumor tissue, such as vacuolization of cytoplasm, cellular and nuclear membrane destruction, activation of apoptosis. In contrast, miniSOG-expressing tumors displayed no reaction to PDT, presumably due to the lack of FMN cofactor needed for fluorescence recovery of the flavoprotein. The results are of interest for photodynamic therapy as a proof of possibility to induce photodamages in cancer cells in vivo using genetically encoded photosensitizers.

Objective: Demonstration of whether a low dose of mTHPC (temoporfin , Foscan) is sufficient to induce an efficient clinical response in palliative PDT of non-resectable cholangiocarcinoma (CC), while showing a low side effect profile as compared to the standard Photofrin PDT. Materials and Methods: 13 patients (14 treatment sessions) with non-resectable CC were treated with stenting and PDT (3 mg Foscan per treatment, 0.032—0.063 mg/kg body weight, 652 nm, 50 J/cm). Fluorescence measurements were performed with a single bare fiber for 5/13 patients prior to PDT at the tumor site to determine the fluorescence contrast. For another 7/13 patients, long-term fluorescence-kinetics were measured on the oral mucosa to determine the time of maximal relative fluorescence intensity. Results: Foscan fluorescence could clearly be identified spectroscopically as early as 20 hours after administration. It was not significantly different between lesion and normal tissue within the bile duct. Fluorescence kinetics assessed at the oral mucosa were highest at 72-96 hours after administration. The DLI was therefore extended from 20 hours to approx. 70 hours for the last 5 patients treated. The treatment effect was promising with a median survival of 11 months for the higher grade tumors (Bismuth types III and IV). Local side effects occurred in one patient (pancreatitis), systemic side effects were much reduced compared to prior experience with Photofrin. Conclusion: Combined stenting and photodynamic therapy (PDT) performed with a low dose of Foscan results in comparable survival times relative to standard Photofrin PDT, while lowering the risk of side effects significantly.

Photodynamic Therapy offers multiple advantages to treat nonmelanoma skin cancer compared to conventional treatment techniques such as surgery, radiotherapy or chemotherapy. Among these advantages are particularly relevant its noninvasive nature, the use of non ionizing radiation and its high selectivity. However the therapeutic efficiency of the current clinical protocol is not complete in all the patients and depends on the type of pathology. Emerging strategies to overcome its current shortcomings include the use of nanostructures that can act as carriers for conventional photosensitizers and improve the treatment selectivity and provide a controlled release of the photoactive agent. In this work, a model for photodynamic therapy combined with gold nanocarriers for a photosensitizer commonly used in dermatology is presented and applied to a basal cell carcinoma in order to predict the cytotoxic agent spatial and temporal evolution.

Retinal photocoagulation is an established treatment for various retinal diseases. The temperature development during a treatment can be monitored by applying short laser pulses in addition to the treatment laser light. The laser pulses induce thermoelastic pressure waves that can be detected at the cornea. We present a numerical model to examine the temperature development during the treatment as well as the formation and propagation of the ultrasonic waves. Using the model, it is possible to determine the peak temperature during retinal photocoagulation from the measured signal, and investigate the behaviour of the temperature profile and the accuracy of the temperature determination under varying conditions such as inhomogeneous pigmentation or change in irradiation parameters. It was shown that there is an uncertainty of 2.5 -9% in the determination of the peak temperature when the absorption coefficient between the absorbing layers is varied by a factor of 2. Furthermore the model was extended in order to incorporate the photoacoustic pressure generation and wave propagation. It was shown that for an irradiation pulse duration of 75 ns the resulting pressure wave energy is attenuated by 76 % due to frequency dependent attenuation in water.

The theory of photo-thermal and photo-mechanical effects in absorbing media under action of short laser pulses has been developed based on numerical solution of motion equations for continuous media in the Lagrange form and heat transfer equation.

Introduction: Ureteric stenting is a commonly used endourologic procedure for temporary and long-term drainage of an obstructed upper urinary tract. The indication for ureteric stenting is obstruction due to intrinsic (intraureteral stones, strictures, or tumors) or extrinsic (for example compressing pelvic or retroperitoneal mass) causes. Despite the fact that stents do certainly have proven benefits in all fields of urology, there are potential morbidities. The most common problem of indwelling ureteral stents is infection. As foreign body in the urinary system, stents act as a nidus for bacteria colonization, crystallization and encrustation. Bacteria induced biofilm formation predisposes for the crystallization of lithogenic salts, such as calcium-phosphate, calcium-oxalate, magnesium-phosphate on the surface initiating stent encrustation. It was the objective of this study to evaluate whether optical coherence tomography (OCT) using both the surface and the endoluminal technique is feasible to investigate the locations and degree of encrustation process in clinically used ureteral stents. Patients and methods: After removal from patients, fourteen polyurethane JJ stents were investigated. A fresh JJ served as a control. The external surfaces were examined using an endoscopic surface OCT whereas the intraluminal surfaces were investigated by an endoluminal radial OCT device. The focus was on detection of encrustation or crystalline sedimentation. Results: In 12 female and 2 male patients, the median indwelling time of the ureteral catheter was 100 days (range 19- 217). Using the endoluminal OCT, the size and grade of intraluminal encrustation could be expressed as a percentage relating to the open lumen of the reference stent. The maximum encrustation observed resulted in a remaining unrestricted lumen of 15-35% compared to the reference. The luminal reduction caused by encrustation was significantly higher at the proximal end of the ureteral stent as compared to its distal part. The extraluminal OCT-investigations facilitated the characterization of extraluminal encrustation. Conclusion: OCT techniques were feasible and facilitated the detection of encrustation of double pigtail catheters on both the extra and intra luminal surface. Quantitative expression of the degree of intraluminal encrustation could be achieved, with the most dense and thickened occurrence of intraluminal incrustation in the upper curl of the JJ stent.

Optical techniques for treatment and characterization of biological tissues are revolutionizing several branches of medical praxis, for example in ophthalmology or dermatology. The non-invasive, non-contact and non-ionizing character of optical radiation makes it specially suitable for these applications. Optical radiation can be employed in medical ablation applications, either for tissue resection or surgery. Optical ablation may provide a controlled and clean cut on a biological tissue. This is particularly relevant in tumoral tissue resection, where a small amount of cancerous cells could make the tumor appear again. A very important aspect of tissue optical ablation is then the estimation of the affected volume. In this work we propose a complete predictive model of tissue ablation that provides an estimation of the resected volume. The model is based on a Monte Carlo approach for the optical propagation of radiation inside the tissue, and a blow-off model for tissue ablation. This model is applied to several types of dermatological tumoral tissues, specifically squamous cells, basocellular and infiltrative carcinomas. The parameters of the optical source are varied and the estimated resected volume is calculated. The results for the different tumor types are presented and compared. This model can be used for surgical planning, in order to assure the complete resection of the tumoral tissue.

A blue-LED photocoagulator device was designed in order to induce a selective photocoagulation effect in superficial bleeding. An in vivo study in rat back skin evidenced an improved healing process in the LED treated abrasions.

In this work we analyze the impact of linear birefringence on biological tissues depolarization, which is essential for correctly interpreting experimental results. Our approach is based on the polarized light Monte Carlo method in transmission. We present a comparative analysis of light depolarization in biological tissues with different values of linear birefringence and particle sizes, in order to evaluate its impact on the calculated parameters.

Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive–refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3^rd and the 5^th harmonic of a Q-switched Nd:YAG laser (λ=355 nm and λ=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at λ=213 nm reveal a smooth optical surface on the intraocular lens with no irregularities, observed with other wavelengths.

Silver nanoparticles are promising product of nanotechnology with attractive physicochemical and biological properties. The main aim of the study was to investigate optical properties of functional silver nanoparticles with different composite agents: polyvinylpyrrolidone, bovine serum albumin, hyaluronan and to explore their potential using in reproductive medicine. The date obtained in the study showed that surface modification of nanoparticles leads to change of their optical, physicochemical and biological properties. The optical properties of silver nanoparticles display, that AgNPs with PVP and BSA is most stable in PBS than AgNPs with HA. However the absorption curves after 120 hours of storage show, that AgNPs-HA were the most stable in ethanol. Results show, that silver nanoparticles did not effect on sperm viability and motility, but cause a changes of some biochemical parameters of conditioned medium, particular increase the concentration of triglycerides, activity of alkaline phosphatase, lactate dehydrogenase and decrease the activity of aspartate aminotransferase and alanine aminotransferase after 3 h of in vitro cultivation at 37°C. According to our latest data AgNPs with HA have a less toxic effect on biological processes in rabbits sperm compared with AgNPs with PVP and BSA. Nevertheless all functional composites of silver nanoparticles at the concentration of 0.1 μg/mL have no toxic effect on spermatozoa and can be successfully applied in reproductive medicine at low concentrations as signal enhancers, optical sensors, and biomarkers.