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At least 271 records · Page 15Linked to original sources
PubMed1990

[Histopathological study of wound healing process of rat tongue and femur by excimer laser irradiation--possibility of cutting of vital tissue by laser irradiation].

The possibilities of bone and soft tissue ablation without thermal damage by 248 nm KrF excimer laser irradiation were examined. A defect was made on the rat tongue by laser at pulse width: 15 nsec, power density: 12 W/cm2, pulse repetition rate: 20 Hz and irradiated time: 60 seconds. The same size defect was made by stainless steel surgical knife for control. The tongues were examined histopathologically at timed sequence from 1 hour to 7 days after operation. The rat femur was cut by laser at pulse width: 15 nsec, power density: 2.6 kW/cm2, pulse repetition rate: 30 Hz and irradiated time: 3 minutes. The femur was amputated by dental diamond disc for control. The femurs were examined histopathologically at timed sequence from 1 hour to 16 weeks after operation. The rat tongue was easily excised with little thermal injury by laser irradiation, and its healing process is almost the same as that of the control. The laser irradiation had no hemostatic effect. The femur could be amputated by laser irradiation but its wound healing was prolonged. The laser ablation stump showed massive necrosis probably due to the thermal injury and these necrotic bones likely disturbed the wound repair. The degree of the thermal injury by the excimer laser irradiation might depend on the irradiation condition because the condition of bone amputation was stronger than that of tongue excision.

Animals↗
PubMed1999

[Laser phacoemulsification with the Paradigm Photon Laser. Surgical technique and first results].

Early clinical results and personal experience with a new technique in cataract surgery using Paradigm Photon Laser (neodymium Yag Laser) are reported. After the introduction of phako ultrasound in cataract surgery, Eichenbaum et al. examined the use of a laser system to improve cataract surgery. A phase I clinical trial was started in the USA in 1996 and a phase II clinical trial is currently ongoing. The Laser technique was performed as follows. A clear corneal incision measuring 2.8 mm, capsulorrhexis, hydrodissection and hydrodelineation of the nucleus and the epinucleus were performed first. A chopping instrument was then introduced by a second port to facilitate the laser procedure. Finally, the incision was enlarged to introduce the foldable IOL in the bag without suture. Eight eyes of six patients with a soft cataract were operated by Nd:YAG Laser, and followed for 6 to 10 months. No particular difficulty was observed concerning the technical procedure in comparison with the phako ultrasonic procedure. Photon laser may be an alternative treatment for softer cataracts with the following advantages: the vulnerability of the posterior capsule to the sharp needle of the phako ultrasonic instrument is eliminated using Photon Laser. There is no propensity for incisional burns nor ultrasonic vibration. However, additional progress is required for its application in hard cataract cases.

Equipment Design↗
PubMed2001

[Laser pointer and laser safety standard].

BACKGROUND: In recent years, cheap laser pointers have been used as toys for children. The safety of laser pointers has become a public issue. CASES: Many cases of visual disturbance without retinal symptoms were reported, and those might be of a psychogenic nature or due to afterimage effects. However, four cases of macular retinal pigment epithelial disturbances due to radiation of a laser pointer beam were reported. One patient was affected in both eyes because of alternate laser beam radiation to both eyes. The exposure time to the laser beam exceeded 10 seconds. All cases except one were young patients. For the safety, it is important that handheld laser pointers be kept away from children. Toy type laser pointers should be treated as Class 1 laser products according to the Consumer Affairs Council, Ministry of Economy, Trade, and Industry.

Consumer Product Safety↗
PubMed2003

Laser flap delay: comparison of Erbium:YAG and CO2 lasers.

The delay phenomenon has long been recognized as a powerful tool in reconstructive surgery. This phenomenon involves creating alterations in skin flap blood supply or microcirculation to increase the size of the surviving flap. In the past many reconstructive surgeons depended on surgical delay as an integral part of their surgical planning. Today surgical delay remains a reliable method for maximizing flap survival. Although surgical delay remains the gold standard many have searched for methods to create the same effect with less morbidity and reduced cost. The purpose of this study was to determine whether near-scarless delay can be performed with either the Erbium:YAG or CO2 laser using a standard McFarlane skin flap model. Four groups were identified. Surgical delay, Erbium laser delay, and CO2 laser delay groups were each compared with a nondelayed control. Each group consisted of ten Sprague-Dawley rats. On Day 0 all delay procedures were performed on the lateral periphery of the outlined dorsal skin flaps. Interruption of this lateral blood supply was accomplished by two parallel 10-cm incisions in the surgical delay group. Likewise blood supply and microcirculatory alterations were accomplished in the laser delay groups by two parallel 10-cm laser treatments. On Day 7 a 10 x 4-cm cranially based dorsal skin flap was elevated. On Day 14 flap survival was analyzed by calculating percentage flap survival. The Erbium:YAG laser delay of the McFarlane flaps resulted in an average of 32 per cent less flap loss compared with controls (P = 0.0001). The CO2 laser resulted in an average of 36 per cent less flap loss compared with controls (P = 0.0002), whereas the surgical delay group had a 23 per cent smaller flap loss (P = 0.009). There was no significant difference between any of the delay groups. These results indicated that CO2 and Erbium:YAG lasers are as effective as surgery for delay of skin flaps in the rat model. They may provide an effective and inexpensive method for near-scarless skin flap delay in humans.

Animals↗
PubMed1992

[Laser photocoagulation of experimentally produced choroidal neovascularization. 2. Comparison of effects by dye and argon blue-green lasers].

Choroidal neovascularization was produced in 18 eyes of 12 rhesus monkeys by application of intense krypton laser photocoagulation. Eight weeks or later, a total of 34 choroidal neovascularizations were treated either by dye laser at wavelengths of 577 or 630 nm or by argon blue-green laser. The treated lesions were evaluated clinically and histopathologically from 24 hours to 3 months after treatment. All the treated lesions were apparently healed by each of the 3 laser modalities. Histopathologically, all the treated choroidal neovascularizations were occluded 24 hours after treatment. At 2 weeks to 3 months after treatment, newly-formed choroidal vessels were present in 3 of 9 lesions (33%) after 577 nm dye laser treatment, in 8 of 9 lesions (89%) after 630 nm dye laser treatment, and in 5 of 8 lesions (62%) after argon blue-green laser. These results seemed to show the clinical superiority of 577 nm dye laser in treating choroidal neovascularization.

Animals↗
PubMedDate not supplied

Primary tooth enamel surface topography with in vitro argon laser irradiation alone and combined fluoride and argon laser treatment: scanning electon microscopic study.

PURPOSE: The purpose of this descriptive scanning electron microscopic study was to characterize surface alterations in primary tooth enamel after in vitro argon laser irradiation alone and combined with topical fluoride treatment either before or after argon laser irradiation. METHODS: Twenty extracted or exfoliated primary teeth underwent soft tissue debridement and a fluoride-free prophylaxis. Buccal and lingual surfaces were determined to be caries-free by macroscopic examination (stereo-zoom binocular microscope, x16). Treatment groups were: (1) no-treatment control; (2) argon laser irradiation (ALI; 11.5 J/cm2); (3) 1.23% acidulated phosphate fluoride (APF before ALI); and (4) ALI before APF. Both buccal and lingual surfaces were evaluated following standard scanning electron microscopic preparation techniques. RESULTS: With controls, enamel surfaces were relatively smooth with occasional enamel prism ends present on their surfaces. There were no areas with cavitations or surface defects. With ALI, the lased surfaces were roughened mildly to moderately irregular without cavitation of the enamel or exposure of enamel prism ends. The surfaces possessed adherent granules to globules, with most being <3 microm in greatest dimension. Only occasional fine cracks and porosities in the surface coatings were noted and these were typically less than 1 microm in width or diameter. With APF before ALI, the surfaces possessed an irregular contour, with numerous granules to globules varying in size from 1 to 3 microm in greatest dimension. With ALI before APF, a homogenous confluent surface was present that masked typical enamel surface markings. The previously noted adherent granules and globules with argon laser treatment alone or APF before ALI were not seen. The argon laser effects on the enamel surfaces were masked by the uniformity of these surface coatings. CONCLUSIONS: Argon laser irradiation and combined APF and argon laser treatment of primary tooth enamel created surfaces that may provide a protective barrier against a cariogenic attack. The surface coatings associated with combined APF and argon laser treatment may contain fluoride-rich calcium and phosphate mineral phases that could act as reservoirs for fluoride, calcium, and phosphate and provide a certain degree of protection from a caries lesion challenge.

Acidulated Phosphate Fluoride↗
PubMed1991

Reflection of CO2 laser radiation from laser-resistant endotracheal tubes.

To assess the possibility of indirect damage by CO2 laser reflection from specialized or modified tracheal tubes, four different tracheal tubes were studied. They were (1) a Rusch red rubber tracheal tube wrapped with 3M No. 425 aluminum foil tape, (2) a Rusch red rubber tracheal tube wrapped with Venture copper foil tape, (3) a polyvinylchloride tracheal tube wrapped with Laser-Guard protective coating, and (4) a Mallinckrodt Laser-Flex tracheal tube. The tracheal tubes were straightened and centered within cardboard cylinders and the laser set to 40 W was aimed to reflect from the tracheal tubes onto the cardboard. The times to combustion perforating the cardboard cylinders because of laser reflection were 1.41 +/- 0.54 (mean +/- SD), 1.73 +/- 0.93, 3.70 +/- 2.18, and 9.26 +/- 3.40 s for tracheal tubes 1, 2, 3, and 4, respectively. The differences between the times to combustion with tracheal tubes 3 and 1, 3 and 2, 4 and 1, 4 and 2, and finally, 4 and 3 were statistically significant. We conclude that the Laser-Guard-wrapped polyvinylchloride tracheal tube and the Mallinckrodt Laser-Flex tracheal tube were less reflective of incident CO2 laser radiation than the copper or aluminum-foil-wrapped red rubber tracheal tubes.

Carbon Dioxide↗
PubMed1993

Laser sclerostomy ab externo using mid infrared lasers.

An ab externo fistulizing procedure (sclerostomy) was performed in vivo in 48 rabbit eyes using a pulsed (20 microseconds and 200 microseconds) Holmium:YAG (Ho:YAG) laser (2120 nm) and a pulsed (200 microseconds) Erbium:YAG (Er:YAG) laser (2940 nm). The laser energy was delivered via an infrared transmitting fiber in contact with the sclera, with the fiber inserted into a specially sharpened retractable cannula in order to guide it into the subconjunctival space. An additional optical fiber-fiber coupling system was required for the Er-YAG laser. A patent fistula (200-micrometers diameter) with formation of a filtering bleb and marked intraocular pressure reduction was achieved in nearly all cases. Significant intraoperative or postoperative complications occurred only with the 20-microsecond Ho:YAG laser. Trauma to the conjunctiva was as minimal as in a subconjunctival injection. The Er:YAG laser created a smaller thermal damage zone at the fistula walls and required significantly less laser energy than the Ho-YAG laser.

Animals↗
PubMed1997

A patient's questionnaire evaluation of krypton laser treatment of facial telangiectases. A comparison with the copper vapor laser.

BACKGROUND: Facial telangiectasia is a common disfiguring condition in modern society. Recently the krypton laser has been advocated as an effective modality for treatment of facial telangiectasia. OBJECTIVE: To compare the effectiveness and incidence of adverse effects of the krypton laser with that of the copper vapor laser in the treatment of facial telangiectasia. METHODS: Two hundred consecutive patients treated with the krypton laser were asked to complete a questionnaire evaluating the treatment; 149 (74.5%) patients responded. RESULTS: The krypton laser was as effective as the copper vapor laser in treating facial telangiectasia. In addition, there was a significant reduction in pain experienced and the incidence of adverse effects was reduced in patients treated with the krypton laser. CONCLUSION: Selection of pulse duration to approximate the thermal relaxation time of the target blood vessel is critical in minimizing adverse effects of laser photocoagulation to facial telangiectases.

Cicatrix↗
PubMed2005

Production of ultrafine particles by nanosecond laser sampling using orthogonal prepulse laser breakdown.

The particle size distribution and composition of nanosecond laser-generated aerosols from brass samples in atmospheric argon has been measured by low-pressure impaction and subsequent quantitative analysis of the aerosols by total reflection X-ray fluorescence. Ablation was performed applying a Nd:YAG laser at 1.06 microm both without and with a prepulse plasma breakdown generated by a second Nd:YAG laser at 2-60 micros prior to the ablation pulse. The beam of the prepulse laser had orthogonal direction to the ablation laser beam, and the breakdown was produced 2.5 mm above the ablation spot. Ultrafine aerosol particles (<50 nm) were generated in the double-pulse experiment representing practically the total mass impacted, while in single-pulse ablation the proportion of large particles (>0.1 microm) was dominating. The predominance of ultrafine aerosols in the prepulse experiment indicates that particle formation from vapor-phase condensation is the major mechanism, while the appearance of large particles in single-pulse ablation points at fragmentary evaporation in the laser-produced plasma. It was also shown that the total mass impacted in double-pulse ablation increases almost linearly with the power of the prepulse laser. The better atomization and the larger sample mass ablated can be assumed to be the main reasons for the increase of the line intensities in double-pulse laser-induced breakdown spectrometry with orthogonal prepulses reported by several research groups.

Journal Article↗
PubMed2004

Frequency-shifted optical feedback in a pumping laser diode dynamically amplified by a microchip laser.

Compared with conventional optical heterodyne detection, laser optical feedback imaging (LOFI) allows for a several orders of magnitude higher intensity modulation contrast. The maximum contrast amplification is typically 10(3) for a diode laser in the gigahertz range and 10(6) for a microchip laser in the megahertz range. To take advantage of the wavelength tunability of a laser diode and of the lower resonant detection frequency of a microchip laser, we used LOFI modulation induced by the frequency-shifted optical feedback in a laser diode as a modulated pumping power for a microchip laser for resonant dynamic amplification. In this way, we were able to transfer the optical feedback sensitivity of the laser diode to the megahertz range. Application to telemetry is also reported.

Journal Article↗
PubMed2004

Microfluidic laser embedded in glass by three-dimensional femtosecond laser microprocessing.

Microfluidic dye lasers three-dimensionally embedded in glass have been fabricated for what is believed to be the first time by integrating micro-optical and microfluidic components by use of a femtosecond laser. By pumping the microfluidic laser, in which the microfluidic chamber was filled with the laser dye Rhodamine 6G dissolved in ethanol, with a frequency-doubled Nd:yttrium aluminum garnet laser, lasing action was confirmed by analysis of the emission spectra at different pump powers. In addition, by arranging two microfluidic chambers serially in the glass, we built a microfluidic twin laser that produces an array of two simultaneous laser emissions with one pump laser.

Journal Article↗
PubMed1996

Alteration of laser-tissue interaction with the 805 nm diode laser using indocyanine green in the canine prostate.

BACKGROUND AND OBJECTIVE: Research interests in laser prostatectomy continue to evaluate a variety of wavelengths and treatment parameters in an effort to optimize treatment. Recently, a semiconductor diode laser with a wavelength of 805 nm has become available for clinical use; however, free-beam noncontact applications were limited by the low power output (25 W). In this study in the canine prostate, the possible potentiating effects of intravenously administered indocyanine green (ICG) were evaluated with the 805 nm diode laser. STUDY DESIGN/MATERIALS AND METHODS: A total of 16 fixed position, free-beam lasings were performed at 25 W for 60 sec in four dogs with eight lasings before and eight lasings after ICG administration. Endoscopic observations and measurements of lesion volumes were used to evaluate the laser-tissue interactions. RESULTS: Prior to ICG administration, we observed that side fire irradiation produced primarily small coagulative lesions. Following ICG administration, however, immediate and more noticeable tissue vaporization occurred, although total lesion size was not increased. Pathologic review demonstrated less coagulation and hyperemia, but a larger vaporized cavity in the ICG treated tissue. CONCLUSION: These findings suggest intravenous ICG alters laser-tissue interaction with the 805 nm diode laser in the canine prostate. The use of the 805 nm diode laser with enhancing chromophores deserves further investigation.

Animals↗
PubMed1999

Laser transmission through membranes using the Q-switched Nd:YAG laser.

BACKGROUND AND OBJECTIVE: Many laser centres utilise various transparent membranes during treatment sessions with Q-switched lasers to prevent or reduce tissue splatter, thereby reducing the aerosolised biohazard of cellular debris to operator and laser. STUDY DESIGN/MATERIALS AND METHODS: We performed a series of experiments with the Q-Switched Nd:YAG laser, a selection of 11 varieties of membrane and a power meter in order to ascertain which of the membranes was the most effective protector concerning transmission of laser energy. Other mechanical properties such as transparency, strength, ease of application, and flexibility were taken into account. RESULTS: Tegaderm (overall average 94% transmission), Cling Film (93%), Bioclusive (89%), Opsite (91%), and Microwave Cling Film (87%) all consistently performed well in pure transmission terms, whereas other membranes tested such as Acetate (74%), Grades of Melinex (75%, 72%, 75%), 2nd Skin (74%), and Perspex (68%) were unsuitable as protection. CONCLUSION: Cling Film proved to be the best all round membrane. We recommend its use for operator and laser protection against the tissue spatter produced from the Q-Switched Nd:YAG laser.

Citrates↗
PubMed2003

Two-laser infrared and ultraviolet matrix-assisted laser desorption/ionization.

Matrix-assisted laser desorption/ionization (MALDI) was performed using two pulsed lasers with wavelengths in the IR and UV regions. A 10.6 micro m pulsed CO(2) laser was used to irradiate a MALDI target, followed after an adjustable delay by a 337 nm pulsed nitrogen laser. The sample consisted of a 2,5-dihydroxybenzoic acid matrix and bovine insulin guest molecule. The pulse energy for both of the lasers was adjusted so that the ion of interest, either the matrix or guest ion, was not produced by either of the lasers alone. The delay time for maximum ion yield occurs at 1 micro s for matrix and guest ions and the signal decayed to zero in approximately 400 micro s. A mechanism is presented for enhanced UV MALDI ion yield following the IR laser pulse based on transient heating.

Animals↗
PubMed2002

Comparison of laser speckle and laser Doppler perfusion imaging: measurement in human skin and rabbit articular tissue.

Laser Doppler perfusion imaging (LDI) is currently used in a variety of clinical applications, however, LDI instruments produce images of low resolution and have long scan times. A new optical perfusion imager using a laser speckle measurement technique and its use for in vivo blood flow measurements are described. Measurements of human skin and surgically exposed rabbit tissue made using this instrument were compared with a commercial laser Doppler perfusion imaging instrument. Results from blood flow measurements showed that the laser speckle imager measured an 11-67% decrease in blood flow under arterial occlusion. Under similar conditions, the laser Doppler imager measured blood flow decreases of 21-63%. In comparison with LDI, it was observed that the higher temporal resolution of the laser speckle imager was more sensitive to measuring the hyperaemic response immediately following occlusion. This in vivo study demonstrated some of the several advantages laser speckle imaging has over conventional LDI, making the new instrument more versatile in a clinical environment.

Animals↗
PubMed1999

The effect of excimer laser photorefractive keratectomy for myopia on nerve fiber layer thickness measurements as determined by scanning laser polarimetry.

OBJECTIVE: Scanning laser polarimetry measures the retardation of polarized laser light as it passes through the birefringent retinal nerve fiber layer (RNFL). Because retardation is directly proportional to the number of retinal nerve fibers, indirect measurements of the RNFL thickness are obtained. A fixed compensatory mechanism is used to correct for retardation attributed to birefringence in the cornea and anterior segment. Excimer laser photorefractive keratectomy (PRK) corrects myopia by ablating tissue from the cornea. This study was conducted to determine the effect of this ablation on RNFL measurements. DESIGN: Prospective comparative case series. PARTICIPANTS: Eighteen patients. METHODS: Patients undergoing PRK had RNFL measurements performed with the GDx Nerve Fiber Analyzer (Laser Diagnostic Technologies, San Diego, CA), a scanning laser polarimeter, in both eyes before and 90 days after PRK in the first eye. MAIN OUTCOME MEASURES: Fourteen different GDx parameters were analyzed for statistically significant differences preoperatively and 3 months postoperatively in the treated and untreated eye using Hotelling's T-squared generalized means test. RESULTS: Eighteen patients underwent PRK in the nondominant eye first. Preoperative refractions averaged -3.8+/-1.6 diopters (D), with an average correction of 3.4+/-1.9 D, corresponding to 49.7+/-20.5 microns of ablation. There were no statistically significant preoperative differences between the fellow eyes in refractive error (P = 0.65). Postoperatively, there were no statistically significant changes in any GDx parameter in the treated eye compared with the untreated control eye (P = 0.21). CONCLUSIONS: Excimer laser PRK for moderate myopia has no significant effect on RNFL thickness measurements as determined by scanning laser polarimetry.

Adult↗
PubMed2002

Speed of particles ejected from animal skin by CO2 laser pulses, measured by laser Doppler velocimetry.

During ablation of tissue with laser pulses rapid sublimation of matter occurs and high pressures are exerted within the tissue, resulting in steam. smoke and particles being expelled. In this paper we report the speed of particles ejected from animal tissue exposed to CO2 laser pulses measured directly by laser Doppler velocimetry (LDV). Speeds recorded just above animal skin were in the range of 9 to 18 m s(-1) for laser pulses of 128 to 384 J cm(-2) respectively. Aerodynamic turbulence slowed the particles down to a critical speed Vc of 4 m s(-1) within a few millimetres above the laser ablation site. Once the particles reach this minimum speed, if no collisions occur, they will only decelerate by gravitational action and the residual kinetic energy will send the particles up to about 0.87 m from the skin surface. Since ejected particles may carry viable cells, acting as disease vectors during laser surgery, our results suggest that the LDV technique should be used to measure the speed of particles ejected from healthy or pathological human tissues, helping to establish safe conditions during laser surgery.

Animals↗