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PubMed1993

Confocal laser scanning ophthalmoscope. Reproducibility of optic nerve head topographic measurements with the confocal laser scanning ophthalmoscope.

BACKGROUND: Glaucoma is an optic neuropathy in which changes in the appearance of both the optic nerve head and the surrounding tissues are important in both diagnosing its presence and progression. Accurate methods to objectively document the appearance of the optic nerve are necessary. The confocal laser scanning ophthalmoscope (Zeiss) is a new prototype instrument that may have the capability to accurately perform this function. METHODS: The authors performed a prospective pilot study evaluating the ability of the confocal laser scanning ophthalmoscope to reproduce three-dimensional optic nerve images. Each retinal image contained 600,000 bytes of information. Thirty discrete images of the right optic nerves of 19 visually normal volunteers were obtained. Depth measurements were compared from the same 100 x 100 micron areas (neighborhoods). RESULTS: Image comparisons found the variability of depth measurements for the entire image were within 102 microns (95% confidence interval). Sixty percent of the depth measurements were reproducible within 100 microns. Variability of the depth measurements was greatest where the neuroretinal rim sloped at the edge of the optic cup and lowest in the peripapillary area. CONCLUSION: The confocal laser scanning ophthalmoscope has the potential to be a safe, rapid, and reproducible method of imaging ocular structures.

Adult↗

PubMed1998

Laser blepharoplasty and laser resurfacing of the periorbital area.

Although blepharoplasty has long been the traditional method of improving the aesthetic appearance of the eyelid area, it yields little improvement in several of the major signs of periorbital aging including (1) wrinkling of the infrabrow and lower lid skin, (2) crow's foot wrinkles, (3) malar bags and wrinkles, (4) crepey changes in the periorbital skin texture, (5) pigment spots and other actinic damage, (6) elongation of the apparent vertical height of the lower lid, and (7) loss of the gentle, indistinct transition between the lower lid and cheek skin. All of these indications can be improved by the combination of laser blepharoplasty and laser resurfacing of the periorbital region. In addition to resurfacing, the author prefers to use the laser for the incisional aspects of the blepharoplasty, as it is quick, causes less sensory nerve stimulation, is less likely to damage the inferior oblique muscle, and has essentially no bleeding--and therefore, less ecchymosis--postoperatively. This technique is described and illustrated photographically. Its outcomes include a high-quality result that maintains itself well over time, improvement in the signs of periorbital aging not treated by traditional blepharoplasty, a low rate of complication, and high patient satisfaction.

Blepharoplasty↗

PubMed1997

[Laser scanning laser ophthalmoscopy in diagnosis of juvenile glaucoma cases with myopia].

UNLABELLED: The diagnosis of the open angle glaucoma in myopic eyes remains one of the major problems, as the changes of the optic head in myopia may be similar to glaucomatous changes. The aim of the study was to analyse biomorphometric parameters of the optic nerve head in myopic eyes with glaucoma with scanning laser ophthalmoscope from Laser Diagnostic Technologies Inc. There was 29 children examined and among them 12 children with glaucoma and myopia as a study group (I) and 17 children with myopia as a control group (II). RESULTS: TCA means values; group I: 1.994 +/- 0.158, group II:2.028 +/- 0.200 CD means values; group I; 0.315 +/- 0.072, group II: 0.247 +/- 0.057 Rim means values; group I: 1.366 +/- 0.164, group II: 1.511 +/- 0.136 Vol. A mean values; group I: +0.205 +/- 0.03, group II: +0.83 +/- 0.03 Vol. B mean values; group I: -0.159 +/- 1.608, group II: -0.117 +/- 0.08. Average values of the biomorphometric parameters of the optic nerve head were worse in group I than in group II, but there was not statistical significance between the differences. Scanning laser ophthalmoscopy may be used as very important additional examination in juvenile glaucoma cases with myopia.

Adolescent↗

PubMed1998

[The prevention of inflammatory complications in mandibular fractures by using infrared laser and magnetic-laser radiation].

A total of 102 patients with mandibular fractures were treated by multiple-modality treatment including infrared (IR) laser exposure and magnetic and laser therapy (MT). For monitoring the treatment efficacy and predicting its results, nonspecific defense factors and intensity of free-radical oxidation (FRO) in the saliva were assessed. IR laser and MT by the Uleĭ-2K device stimulated local defense factors, decreased the intensity of salivary FRO, and thus promoted the healing of mandibular fractures.

Adult↗

PubMed2026

Comparison of a 755-nm picosecond laser and a 1565-nm nonablative fractional laser for the treatment of atrophic acne scars: a 20-week prospective, randomized, split-face clinical study.

To compare the efficacy and safety of a 755-nm picosecond laser with a diffractive lens array (P-DLA) and a 1565-nm nonablative fractional laser (NAFL) for the treatment of atrophic acne scars. Twenty-seven patients with atrophic acne scars underwent three sessions of randomized split-face treatment with P-DLA and NAFL at 4-week intervals. Patients were followed up at 1, 2, and 3 months after the final treatment. Efficacy was assessed using the Échelle d'Évaluation Clinique des Cicatrices d'Acné (ECCA) grading scale, the Investigator's Global Assessment (IGA) score, patients' self-rated improvement, and overall satisfaction. Treatment-related adverse reactions were recorded daily by patients until resolution. Both modalities demonstrated significant improvements in scar appearance based on ECCA score, IGA score, and patients' self-rated improvement (P < 0.001). No statistically significant differences in efficacy were observed between the two treatments. However, the P-DLA group showed higher patient satisfaction (P = 0.035) and a more favorable safety profile, including shorter durations of erythema and edema and the absence of crusting. Both P-DLA and NAFL were effective and safe for the treatment of atrophic acne scars, with similar efficacy. P-DLA offered better tolerability.

Humans↗

PubMed2003

Direct detection of particles formed by laser ablation of matrices during matrix-assisted laser desorption/ionization.

We report the detection of nanoparticles formed by irradiating matrix-assisted laser desorption/ionization (MALDI) matrix samples. This is direct evidence for the ejection of large size aggregates in the MALDI process. Nanometer-size particles were generated via a tunable solid-state UV laser, irradiating a sample placed in a nitrogen atmosphere. Size distribution measurements were performed using a differential mobility analyzer and a condensation particle counter. Particles in the 10-1000 nm size range were detected. The dependence of the particle size distribution on the laser fluence, wavelength and matrix was investigated. The observed effects are discussed and related to the MALDI ablation dynamics and gas-phase processes.

Journal Article↗

PubMed2006

Laser desorption/ionization and laser ablation synthesis of new selenium oxide compounds from selenium(IV) dioxide.

Laser desorption/ionization (LDI) and/or laser ablation (LA) of selenium dioxide crystals or its mixtures with sodium peroxide were studied using a commercial matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer. It was found that LDI and LA of selenium (IV) dioxide not only ionizes SeO(2), but also leads to the formation of several positively and negatively singly charged species: SeO(n) (+) (n = 0-2), Se(2) (+), SeO(n) (-) (n = 0-4), Se(2)O(n) (-) (n = 3-7), Se(3)O(n) (-) (n = 4-9), Se(4)O(n) (-) (n = 8-10). A rather high yield of selenium species in the positive ion mode, Se(m) (+) (m = 1-8) and Se(m)OH(+) (m = 3-7), was obtained by using the MALDI approach while the species detected in the negative ion mode, SeO(n) (-) (n = 0-4), Se(2)O(n) (-) (n = 3-7), Se(3)O(n) (-) (n = 4-9), and Se(4)O(n) (-) (n = 9, 10), were the same as those observed during LDI/LA of selenium dioxide. The addition of sodium peroxide to selenium dioxide with the aim of enhancing its oxidation and thus increasing the production of SeO(4) product resulted in extensive cationization of the species with sodium or potassium. The following positively and negatively charged species were identified: Se(+), Se(2) (+), Se(2)OH(+), Se(2)ONa(+), SeO(n) (-) (n = 0-3), and Se(2)O(n) (-) (n = 0, 1, 4). Also observed in mass spectra of such mixtures, various mixed sodium and/or potassium adducts with selenium oxide species, e.g. Se(2)O(4)K(2)Na(-), were identified. In all, 26 totally new species, Se(2)O(n) (-) (n = 3-6), Se(3)O(n) (-) (n = 4-9), Se(4)O(n) (-) (n = 8-10), Se(4)O(11)H(5) (-), Se(4)O(12)H(3) (-), Se(2)O(4)Na(-), Se(2)O(5)HNa(-), Se(2)O(5)HNa(2) (-), Se(3)O(6)K(2)Na(-), Se(3)O(6)K(2)Na(2) (-), Se(2)ONa(+), and Se(m)OH(+) (m = 3-7), were described for the first time. Also, for the first time, the formation of selenium(IV) diperoxide, O-O-Se-O-O or O(2)SeO(2), is described. The stoichiometries of the compounds generated were confirmed using isotopic pattern modeling.

Journal Article↗

PubMedDate not supplied

Spectral characteristics of autofluorescence and second harmonic generation from ex vivo human skin induced by femtosecond laser and visible lasers.

The spectral properties of one-photon, two-photon excited autofluorescence and second harmonic generation (SHG) from ex vivo human skin induced by a femtosecond (fs) laser and three visible lasers in backscattering geometry are systematically investigated. Our experimental results indicate that peak position of autofluorescence spectra from the dermis and epidermis shift toward long wavelengths, and the fluorescent intensity decreases when the excitation wavelength increases due to an effect of the excitation wavelength on autofluorescence signals. However, the intensity of the SHG signal in collagen has the maximal value of 800 nm excitation wavelength. This may be the result that the energy of the SHG signal is in resonance with an electronic absorption band. The two-photon excited autofluorescence and SHG intensity all obey a quadratical dependence on the excitation power. Compared with the two-photon excited fluorescence and SHG, the one-photon excited fluorescence in the dermis and epidermis exhibits different spectral characteristics. The investigation of the spectral characteristics of autofluorescence and SHG from ex vivo human skin can provide new insights into morphologic structures and biochemical components of tissues, which are vital for improving the application of laser-induced autofluorescence and SHG spectroscopy technique for noninvasive in vivo tissue diagnostics.

Epidermis↗

PubMed2003

Laser-induced fluorescence with an OPO system. Part II: direct determination of lead content in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF).

Fluorescence was induced by coupling a laser with an optical parametric oscillator (OPO) to develop an analytical method for the direct determination of lead content, at ultra-trace level, in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). The optimization of atomization conditions, laser pulse energy, and mainly temporal parameters allowed us to reach a 3 fg detection limit (0.3 ng L(-1)) despite the low repetition rate of the device. The expected error on predicted concentrations of lead, at trace levels, in seawater was below 15%.

Journal Article↗

PubMed2000

Laser atomic absorption spectrometry of excited Hg in a discharge applying sum frequency mixing of two diode lasers (preliminary results).

Wavelength modulation diode laser atomic absorption spectrometry is applied to the detection of atomic mercury. Transitions from metastable energy levels highly populated in a radio-frequency discharge are induced with laser diodes by use of nonlinear techniques. The wavelength of one strong transition at 365.119 nm with a high oscillator strength is obtained by sum frequency generation of two diode lasers. The cold vapor technique is used to transfer ionic into atomic mercury. The mercury in the vapor phase is transported by an argon stream into the discharge tube. From the time-dependent absorption signals detection limits of 100 ng/L are achieved at this state of research.

Journal Article↗

PubMed2002

Laser induced decohesion of coatings: probing by laser ultrasonics.

The aim of the present study is to investigate a conventional laser-ultrasonics technique for the determination of intrinsic properties of oxide coatings and their adhesion strength on a metallic substrate. The good agreement between experiments and computations in an epicenter configuration allows determining the longitudinal wave velocity as well as the Young's modulus of the oxide coatings versus the porosity. For a critical value of the laser energy, a breakdown at the coating-substrate interface is generated by the laser irradiation. The critical tensile stress field developed at the coating/substrate interface, which leads to the interfacial fracture, can be easily calculated. The value of the practical adhesion which is defined is found to be in accordance with those obtained by classic contact techniques (tensile adhesion test, indentation, bending test). Finally, this work demonstrates that this quantitative, contactless test fits well to simultaneously characterise the oxide coatings and evaluate the coating-substrate adhesion.

Journal Article↗

PubMed2002

Mathematical modeling of laser ablation in liquids with application to laser ultrasonics.

The use of laser ablation as a means of generating ultrasonic waves in liquid metals is studied in this paper. A mathematical model for predicting the onset of ablation is developed, as is a model of the ablation process based on steady state, one-dimensional gas dynamics in which the vapor phase is treated as an ideal gas. The results of this model are then used in a quasi-two-dimensional model of laser ablation that accounts for the spatial distribution of intensity in the laser beam. Model predictions are compared with experiments conducted on liquid mercury and excellent agreement is obtained. Based on these results, a simplified model is developed that shows excellent agreement with both the theory and the experiments.

Journal Article↗

PubMed1998

Imipramine does not affect argon-laser-induced pin-prick pain thresholds and laser-evoked cerebral potentials.

The tricyclic antidepressant imipramine has shown analgesic effect in human clinical and experimental pain studies. The aim of the present study was to test the effect of imipramine on a pure short-term nociceptive stimulus with pin-prick pain quality. In a randomized, placebo-controlled, double-blind, crossover study, the hypoalgesic effect of a single oral dose of 100 mg imipramine was investigated in 10 healthy volunteers. Test procedures performed before and 2, 4, 6, 8, 10, 12 and 14 h after medication included determination of warmth and pin-prick pain thresholds to high-energy argon laser light stimulation on the hand, as well as laser-evoked cerebral potentials to suprathreshold stimulation. Both the warmth and the pin-prick pain thresholds (p=0.49 and 0.85) and the root mean square of the laser-evoked potentials (p=0.89) were unaltered by imipramine. It is concluded that a single oral dose of 100 mg imipramine has no effect on pin-prick pain. This study demonstrates the important fact that a drug may show clear analgesic effect in some experimental pain models while it is without effect in other models; e.g. imipramine is known to affect pain tolerance and summation thresholds. Pre-clinical tests of potentially analgesic drugs should therefore be based on different pain-stimulation modalities. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.

Journal Article↗

PubMed2001

A mobile mass spectrometer for comprehensive on-line analysis of trace and bulk components of complex gas mixtures: parallel application of the laser-based ionization methods VUV single-photon ionization, resonant multiphoton ionization, and laser-induced electron impact ionization.

A newly developed compact and mobile time-of-flight mass spectrometer (TOFMS) for on-line analysis and monitoring of complex gas mixtures is presented. The instrument is designed for a (quasi-)simultaneous application of three ionization techniques that exhibit different ionization selectivities. The highly selective resonance-enhanced multiphoton ionization (REMPI) technique, using 266-nm UV laser pulses, is applied for selective and fragmentationless ionization of aromatic compounds at trace levels (parts-per-billion volume range). Mass spectra obtained using this technique show the chemical signature solely of monocyclic (benzene, phenols, etc.) and polycyclic (naphthalene, phenathrene, indol, etc.) aromatic species. Furthermore, the less selective but still fragmentationless single photon ionization (SPI) technique with 118-nm VUV laser pulses allows the ionization of compounds with an ionization potential below 10.5 eV. Mass spectra obtained using this technique show the profile of most organic compounds (aliphatic and aromatic species, like nonane, acetaldehyde, or pyrrol) and some inorganic compounds (e.g., ammonia, nitrogen monoxide). Finally, the nonselective ionization technique laser-induced electron-impact ionization (LEI) is applied. However, the sensitivity of the LEI technique is adjusted to be fairly low. Thus, the LEI signal in the mass spectra gives information on the inorganic bulk constituents of the sample (i.e., compounds such as water, oxygen, nitrogen, and carbon dioxide). Because the three ionization methods (REMPI, SPI, LEI) exhibit largely different ionization selectivities, the isolated application of each method alone solely provides specific mass spectrometric information about the sample composition. Special techniques have been developed and applied which allow the quasi-parallel use of all three ionization techniques for on-line monitoring purposes. Thus, a comprehensive characterization of complex samples is feasible jointly using the characteristic advantages of the three ionization techniques. Laboratory applications show results on rapid overview characterization of mineral oil-based fuels and coffee headspace. The first reported field applications include timely resolved on-line monitoring results on automobile exhausts and of waste incineration flue gas.

Journal Article↗

PubMed2003

Elemental fractionation studies in laser ablation inductively coupled plasma mass spectrometry on laser-induced brass aerosols.

Previous investigations on laser-induced aerosols of brass samples showed that preferential vaporization of zinc occurs during the ablation process leading to elemental fractionation and limited possibilities for non matrix matched calibration. In a variety of experiments carried out within this study it is shown that multiple effects are complicating the quantification of brass using IA-ICPMS. It is shown that the ablated copper and zinc is not homogeneously distributed within the laser-produced aerosol. Copper was found enriched up to 100% in particles larger than 100 nm as shown from EDX measurements (electron excited) on individual particles, and zinc was enriched by over 40% in the particles smaller than the lowest measurable particle size (below 100 nm or in the vapor phase). Solution nebulization analysis on digested filter-collected aerosols results in a higher Cu/Zn ratio than the certified value for the brass sample. ESEM pictures with analysis of the electron excited X-rays measured on the filter-collected material support the results showing copper enrichment. However, online LA-ICPMS measurements carried out under the same operating conditions as for filtering show a copper depletion within the ICP, which leads to the conclusion of partial vaporization and ionization of the aerosol particles in the ICP. The larger particles containing more or exclusively copper are not completely ionized. Within this study, three sources of elemental fractionation can be distinguished and described: (A) The ablation process leads to no measurable copper enrichment at the ablation crater rim. (B) Zinc deposition between the ablation site and the aerosol collection on filters leads to an up to 37% higher Cu/Zn ratio on the filter in comparison to the certified value. (C) On-line laser ablation aerosols measured within the ICPMS lead to significantly lower Cu/Zn ratios in comparison to the certified value. (D) Combination of the various studied sources of fractionation can finally lead to an agreement between measured and certified values due to inverse overlapping of various fractionation sources.

Journal Article↗

PubMed2003

Trace level determination of lead in solid samples by UV laser ablation and laser-enhanced ionization detection.

Laser-enhanced ionization was investigated as a detection technique for trace elemental analysis of solid samples by laser ablation. Laser ablation of aluminum samples was performed in an ablation cell, and the ablated material was carried by a flow of gas to a miniature LEI flame where Pb was detected. This decoupling of ablation cell and detector allowed the independent optimization of vaporization and detection processes. We have investigated the different excitation schemes for Pb and uncovered five new LEI-active transitions in the visible range. We have demonstrated that the use of an argon-oxygen/acetylene flame sheathed with argon resulted in the elimination of background interference from the two-photon ionization of nitric oxide. We have shown that the use of helium as a carrier gas results in a higher ablation yield and lower pulse-to-pulse variations in LEI signal and in better analytical figures of merit. We have characterized the performance of the technique in terms of detection limits and dynamic range, and we have obtained a detection limit of 60 ng/g for the determination of Pb in high purity aluminum.

Journal Article↗

PubMed2005

Use of sol-gels as solid matrixes for trace analysis by UV laser ablation and laser-enhanced ionization detection.

Zirconium and silicon sol-gels were investigated as solid materials for trace elemental analysis of pelletized solid samples by laser ablation and laser-enhanced ionization. The highly homogeneous dispersion of an internal standard spiked in the solid material obtained with the sol-gel formation process leads to a significant improvement in signal repeatability and to an increase in the precision of measurements through better correction of variations in the laser ablation rate. Signal repeatability values of 5-8% RSD were obtained for Pb in NIST 1632c Bituminous Coal sample pellets prepared using both sol-gels, as compared to 9-21% for graphite-based sample pellets. Furthermore, the zirconium sol-gel was shown to offer better resilience to signal bias due to preferential ablation and a more accurate correction of ablation rate using the internal standardization method.

Journal Article↗

PubMed2003

[Pseudomelanoma following laser treatment or laser-treated melanoma?].

BACKGROUND: The increasing use of lasers for the removal of pigmented skin lesions has led to a growing risk of erroneously treated malignant melanocytic tumours. PATIENTS AND METHODS: In two patients, both of whom developed a melanoma, the lesions were initially misdiagnosed clinically as a benign naevus and treated with laser vaporisation. RESULTS: On recurrence of the tumours, the diagnosis of melanoma was finally established by histological examination of the excised tumours in which differentiation from pseudomelanoma remained difficult. CONCLUSIONS: In such cases of initially misdiagnosed melanomas, laser removal not only complicates and delays the correct diagnosis but might also worsen the prognosis after recurrence of an incompletely removed tumour.

Adult↗