前立腺レーザー高温度治療におけるNd: YAGパルス波と連続波レーザーの違いに関する基礎的検討

Reduction of laser-induced pathologic tissue injury using pulsed energy delivery

Chemiluminescence test results were used to evaluate the sensitivity of human blood and murine splenocytes to continuous-wave (CW) and pulsed He-Ne laser light. It is demonstrated that CW radiation has in our experimental conditions practically no effect on the luminol-amplified chemiluminescence of four models under study. The pulsed radiation had a week inhibiting effect on the samples from healthy organisms but inhibited markedly the chemiluminescence of samples from tumor-bearing organisms. The effect depended on duration of dark period between pulses. A transient local heating mechanism is proposed to explain the inhibition of activity of NADPH-oxidase.

The strong phototoxicity of the red fluorescent protein KillerRed allows it to be considered as a potential genetically encoded photosensitizer for the photodynamic therapy (PDT) of cancer. The advantages of KillerRed over chemical photosensitizers are its expression in tumor cells transduced with the appropriate gene and direct killing of cells through precise damage to any desired cell compartment. The ability of KillerRed to affect cell division and to induce cell death has already been demonstrated in cancer cell lines in vitro and HeLa tumor xenografts in vivo. However, the further development of this approach for PDT requires optimization of the method of treatment. In this study we tested the continuous wave (593 nm) and pulsed laser (584 nm, 10 Hz, 18 ns) modes to achieve an antitumor effect. The research was implemented on CT26 subcutaneous mouse tumors expressing KillerRed in fusion with histone H2B. The results showed that the pulsed mode provided a higher rate of photobleaching of KillerRed without any temperature increase on the tumor surface. PDT with the continuous wave laser was ineffective against CT26 tumors in mice, whereas the pulsed laser induced pronounced histopathological changes and inhibition of tumor growth. Therefore, we selected an effective regimen for PDT when using the genetically encoded photosensitizer KillerRed and pulsed laser irradiation.

We report on continuous-wave red laser radiation at 669 nm from a self-frequency-doubled laser of YAl3(BO3)4:Nd3+ operating at a fundamental wavelength of 1338 nm in the F3/24→I13/24 laser channel of Nd3+ ion. Main laser characteristics at the fundamental wavelength are investigated as well as second harmonic generation properties. In nonoptimal preliminary experiments, 1 mW of red radiation is obtained for 900 mW pump power from a Ti:sapphire laser.

Modifications and microstructures are generated on the surface and in the volume of silicate glasses using pulsed UV laser radiation of small pulse length. During the interaction of pulsed excimer laser radiation and frequency-trippled Nd:YAG laser radiation with intensities below the removal-threshold of the cerium- and silver-doped multi-component silicate glass absorption centers in the UV are induced. Subsequent thermal treatment and wet chemical etching results in crystallization of the laser-illuminated absorbing region and in the fabrication of microstructures on the surface. Processing of sodalime- and boro-silicate glass with pulsed ArF excimer laser radiation and frequency-doubled Nd:YAG laser radiation with intensities above the removal-threshold leads to microstructures including the generation of microcracks on the surface and in the bulk. The dynamics and the transmission of the expanding plasma and changes in the refractive index of the glass are investigated with speckle photography using the pump and probe method. The determination of plasma emission and crack generation is carried out using high speed and Nomarski photography. Morphological and chemical properties of the debris generated under defined processing gas atmospheres are investigated with REM, white light interferometry, XPS and EPMA. Induced absorption and changes of the crystalline- phase are probed using optical-spectroscopy and XRD as well REM. On the basis of these investigations the processes of the generation of induced absorption centers and crystallization on the one hand and the generation of cracks and debris on the other hand as well as the quality of the produced microstructures is discussed.

Analysis of the signal to noise ratios and processing capacities obtainable with pulsed and continuous wave lasers as sources for Raman detection of diamonds, indicated almost equal performance with two systems of equal average power. It was found, however, that in practical use where the Raman signal has to be distinguished from a competing fluorescence signal at the same wavelength, that the use of a pulsed laser offers a decided advantage for use in diamond detection (ratio Raman to diamond fluorescence were up to 10 times higher with pulsed), due to non-linear response of the fluorescence yield with laser power.

Influence of gold nanolayer coating on the continuous-wave laser ablation of a pure aluminum surface: Evaluations of structural and optical features

Holographic and Speckle Pattern Interferometry utilising continuous wave lasers has so far been useful only as a laboratory tool. A major drawback limiting its introduction to industrial applications is the degree of environmental stability needed to obtain high quality fringes. Application of a pulsed laser to Holographic Interferometry has been demonstrated by several workers to show significant improvement in stability and scope of application. In a similar way, a pulsed laser can produce speckle correlation fringes on a single frame from a CCD TV camera, thus eliminating environmental sensitivity problems and rigid body motion. Results obtained with Electronic Speckle Pattern Interferometry (ESPI) incorporating a pulsed YAG laser are reported. Vibration and static deformation fringes have been produced for a clamped metal plate. With a double pulse laser, the first pulse can he positioned at any time during the vibration cycle. The firing of the second pulse depends on the scanning time of a single field of the CCD camera. Due to the pulsing action of the laser the vibration amplitude fringe pattern can he animated on the TV screen to gain a visual impression of the surface motion. A new technique has been developed for extracting deformation and shape information from interferometric fringes. It involves a significant improvement in environmental stability and reduced computational effort. Problems due to noise and data ambiguity are eliminated with the extraction of phase information from only two digitised interferograms. Continuous wave, stroboscopic and pulsed laser illumination are all amenable to this one technique. Results employing the new fringe processing algorithms are presented. Comparisons are made with data obtained with a computer Finite Element prediction for the same target.

The necessity of increasing the stability of the parameters of pulsed and cw laser radiation when operating at peak powers is substantiated. Particular attention is paid to the parameters of pulsed laser radiation in systems with semiconductor pumping. The main requirement in this case is the repeatability of the parameters of the output pulses with high accuracy. This condition is ensured by the stability of the diode supply drivers, especially at peak powers, which are required for scientific research. It was found that even a short-term excess (about 1 ms) of the upper range of the permissible current leads to damage to the laser diode, which instantly degrades the parameters of laser radiation. The developed technique can significantly reduce the likelihood of these phenomena and increase the reliability of the laser.

The thermodynamic response of soft biological tissues to pulsed ultraviolet laser irradiation

The coagulation effect of a continuous-wave neodymium-YAG (Nd-YAG) laser and of a high-power (500 W) pulsed (3–500 ms) microcomputer-controlled Nd-YAG laser are compared in rat liver in vivo. In a series of 68 animals, surface temperature was measured with an infrared camera, and necrosed volume was assessed histologically 24 h after laser irradiation. The high-power pulsed Nd-YAG laser presents two interesting features. First, it gives a better control of surface temperature. Second, a controlled sequence of high-power short pulses produces a predictable coagulated volume which can be comparable to that obtained with continuous-wave Nd-YAG or argon lasers.

Laser drilling is a very versatile tool to produce high accuracy bores in small and large geometries using different technologies. In large and deep hole drilling laser drilling can be found in drilling cooling holes into turbomachinery components such as turbine blades. In micro drilling, the technology is used for the generation of nozzles and filters. However, especially in macro drilling, the process often causes microstructure changes and induces defects such as recast layers and cracks. The defects are caused by the melt dominated drilling process by using pulse durations in the range of some 100 μm up to a few ms. A solution of this problem is the use of ultrashort pulsed laser radiation with pulse durations in the range of some 100 fs up to a few ps, however with the disadvantage of long drilling times. Thus, the aim of this work is to combine the productive process by using ms pulsed fiber laser radiation with subsequent ablation of existing recast layers at the hole wall by using ultrashort pulsed laser radiation. By using fast scanning techniques the recast layer can be avoided almost completely. With a similar technology also very small hole can be produced. Using a rotating dove prism a circular oscillation of the laser spots is performed and holes are drilled at intervals in 1 mm thick stainless steel (1.4301) by ultra-short laser pulses of 7 ps at 515 nm. The formation of hole and the behavior of energy deposition differ from other drilling strategies due to the helical revolution. The temporal evolution of the hole shape is analyzed by means of SEM techniques from which three drilling phases can be distinguished.

Investigation on phase-modulation characteristics and transmission of the liquid crystal device under continuous-wave laser irradiation

This study was initiated to investigate the effect of pulsed XeCL excimer laser radiation (308 nm) at 25 and 50 pulses per second at radiation levels of 0, 100 mJ, 200 mJ, and 300 mJ on microorganism contamination of in vitro cultures of Heder a canariensis. Explants were cultured on Murashige and Skoog (MS) medium supplemented with 8 mg/BA and 0.2 mg/NAA. The medium was adjusted to pH 5.7. The cultures were maintained for 16-hours photoperiods at 25.5°C. One day following transfer the explants were treated with pulsed excimer laser radiation. The percentage of contamination was reduced by laser radiation treatments. The effect of 5 0 pulses of radiation was found to increase the petiole length, leaf blade width, and leaf number of explants.

The effects of low-intensity near-infra-red laser irradiation (820 nm; 1.5 and 9.0 J cm−2; pulsed at 12 Hz, 73 Hz and 5 kHz) upon peripheral neurophysiology and skin temperature were investigated using antidromic conduction studies in the human median nerve in vivo. Healthy human volunteers (n = 90) were recruited and allocated randomly to either a control group (n=10) or one of eight experimental groups (two radiant exposures, 1.5 J cm−2 and 9.0 J cm−2 at one of three pulse repetition rates, 12 Hz, 73 Hz or 5 kHz, in addition to a placebo group for each radiant exposure;n = 10 all groups). Analysis of variance (ANOVA) demonstrated a significant (p≤0.05) decrease in skin temperature following irradiation at the lowest radiant exposure (1.5 J cm−2) combined with pulse repetition rates of 73 Hz and 5 kHz, with the greatest effect at 73 Hz. These changes in skin temperature were coupled with increases in negative peak latency (NPL); ie changes in NPL were inversely related to changes in skin temperature. However, in contrast to the authors' previous findings using continuous wave (CW) laser irradiation, differences in NPL were not found to be significant. These findings, therefore, provide little evidence of the neuro-physiological effects of low-intensity infra-red irradiation at the dosage levels and pulse repetition rates used here.