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At least 487 records · Page 27Linked to original sources
PubMed1997

Intracranial pressure waves generated by high-energy short laser pulses can cause morphological damage in remote areas: comparison of the effects of 2.1-micron Ho:YAG and 1.06-micron Nd:YAG laser irradiations in the rat brain.

BACKGROUND AND OBJECTIVE: Histological effects of 2.1-micron Ho:YAG and 1.06-micron Nd:YAG laser pulses were compared in the rat brain, with special regard to areas remote from the irradiated site. STUDY DESIGN/MATERIALS AND METHODS: Laser pulses were delivered through a 0.6-mm glass fiber, the tip of which was either introduced into the caudate nucleus (application mode I), or held at a 2-mm distance above the exposed intact dura. In the latter case, the space between the dura and the fiber tip was filled either with physiological saline (application mode II) or with air (application mode III). RESULTS: In application modes I and II, but not in application mode III, Ho:YAG laser pulses of 1.5 J and 200 microseconds, but not Nd:YAG laser pulses with the same parameters, immediately caused morphological damage to a considerable number of neurons and axons randomly distributed among apparently normal ones in certain areas remote from the irradiated site. A decrease in the energy and an increase in the length of the pulses lowered the incidence of the remote morphological damage. CONCLUSION: This novel finding may impose limits on the application of Ho:YAG lasers in human endoscopic neurosurgery.

Animals↗
PubMed1999

Histologic analysis of the thermal effect on epidermal and dermal structures following treatment with the superpulsed CO2 laser and the erbium: YAG laser: an in vivo study.

BACKGROUND AND OBJECTIVE: To compare the in vivo histologic effects of the carbon dioxide (CO2) and erbium:yttrium aluminum garnet (Er:YAG) lasers. To ascertain the effects of combining CO2 and Er:YAG laser modalities during a single treatment session. STUDY DESIGN/MATERIALS AND METHODS: Ten patients underwent laser treatment to four left preauricular sites 7 days prior to rhytidectomy as follows: CO2 alone, CO2/Er:YAG, Er:YAG alone, and Er:YAG/CO2. The right preauricular area was identically treated 1 hour prior to rhytidectomy. Laser treated skin was excised during rhytidectomy and was evaluated histopathologically in a blinded manner. RESULTS: After 7 days, all groups were reepithelialized and showed equal neo-collagen formation. After 7 days, CO2/Er:YAG and Er:YAG alone had the least collagen injury and thickest epidermis and papillary dermis of all groups. Specimens lased 1 hour prior to excision showed the least collagen injury and thermal necrosis when treated with CO2/Er:YAG and Er:YAG alone. Four passes with CO2 removed 250 microm of tissue, while eight passes with the Er:YAG removed 160 microm of tissue. CONCLUSIONS: Limiting CO2 laser passes and ending with Er:YAG produces less collagen injury, less thermal necrosis, and more robust epithelial and dermal fibrous tissue regeneration. CO2 followed by Er:YAG has similar thermal necrosis and collagen injury as Er:YAG alone, presumably due to Er:YAG removal of CO2 induced thermal injury.

Dermis↗
PubMed2000

Recalcitrant molluscum contagiosum in a patient with AIDS: combined treatment with CO(2) laser, trichloroacetic acid, and pulsed dye laser.

BACKGROUND AND OBJECTIVE: Recalcitrant molluscum contagiosum (MC) in patients with acquired immunodeficiency syndrome (AIDS) is usually difficult to treat. We present a case treated by a combination of CO(2) laser, trichloroacetic acid, and the 585-nm pulsed dye laser (PDL). The purpose was to determine the effectiveness and ease of these treatment modalities. STUDY DESIGN/MATERIALS AND METHODS: A patient with AIDS presented with recalcitrant MC lesions, predominantly located on the face. The lesions were first treated with the CO(2) laser, in two sessions. Recurrent lesions were treated either with 50% trichloroacetic acid (TCA) or with the PDL. RESULTS: The CO(2) laser treated lesions healed within 2 weeks without secondary infection. The PDL and the TCA treated lesions resolved completely after one treatment. CONCLUSION: Treatment of MC in AIDS patients remains a challenge. The combination of two or more therapeutic modalities, such as CO(2) laser, PDL, and TCA can be of great help to improve the quality of life of these patients.

AIDS-Related Opportunistic Infections↗
PubMed1989

Laser angioplasty with a pulsed NdYAG laser: early clinical experience.

Since December 1986, 40 laser angioplasty procedures have been performed using the energy from a pulsed NdYAG laser, delivering near infrared light (1064 nm) in 100-microseconds pulses of approximately 300 mJ per pulse, directly through a transparent sapphire tipped device. All patients had total occlusion of the superficial femoral artery and symptoms severe enough to warrant surgery, with ulceration or gangrene in eight, rest pain in 14 and severe claudication interfering with life-style in the others. The device was introduced through an antegrade puncture of the superficial or common femoral artery and laser recanalization was followed by attempted balloon angioplasty in all cases. Occlusions were a median length of 15 cm (range 2-35 cm); ten patients had previously undergone failed attempts at conventional balloon angioplasty and four had occluded femoropopliteal grafts. Thirty-seven legs of 34 patients were treated with an average of 60 J (range 10-235 J) with successful recanalization in 27 and immediate reocclusion in seven. The 20 successful recanalizations have been followed up for up to 24 months (median 7 months) with only one late occlusion at 5 months. Failed recanalization was due to poor transmission by the delivery device in the early part of the series (five cases), repeated passage of the device down a collateral branch (four cases), dissection at the site of previous surgery (two cases) or no apparent reason (two cases). Immediate reocclusion was due to very poor run off in patients with severely ischaemic limbs (three cases) or technical difficulties with balloon dilatation (two cases). Complete symptomatic relief was obtained in all the cases of radiologically successful laser angioplasty. Early surgery was required in one case following reocclusion of the artery when an angioplasty balloon failed to deflate, and one patient suffered a skin reaction thought to be due to inadequate removal of the sterilizing solution. A different sterilizing procedure is now followed. Laser angioplasty can reduce the number of patients requiring bypass surgery and improvements in the device and access methods may reduce the number of untreatable cases.

Adult↗
PubMed2003

Influence of wavelength on response to laser photothermolysis of blood vessels: implications for port wine stain laser therapy.

BACKGROUND AND OBJECTIVE: Treatment of port wine stains (PWS) by photothermolysis can be improved by optimizing laser parameters. We have studied the all-important role of wavelength (lambda) by performing pulsed laser photothermolysis in the vasculature of the chick chorioallantoic membrane (CAM) assay. STUDY DESIGN/MATERIALS AND METHODS: The CAM contains an extensive microvascular network ranging from capillaries with diameter D < 20 microm to blood vessels of D approximately 120 microm. The CAM assay enables observation and real-time video documentation of blood flow in pre-capillary arterioles (A) and post-capillary venules (V). The ScleroPlus trade mark laser (Candela Corp., Wayland, MA) has a smooth output over its fixed 1.5 ms pulse duration and allows the operator to vary several treatment parameters such as wavelength, spot size, and energy. Blood vessels in the CAM were irradiated at two clinically relevant wavelengths, lambda = 587 or 597 nm, constant spot size (7 mm), and at different exposures (E = 5-12 J/cm(2)). Threshold exposure (E(th)) (at which non-reversible damage occurred) were 5 J/cm(2) at 587 nm and 8 J/cm(2) at 597 nm. Mathematical modeling was developed to interpret initial (within 30 seconds) injury of arterioles and venules at both wavelengths as a function of D when varying E. RESULTS: Vessel injury was graded off-line from videotapes. For all combinations of lambda and E, measurable injury was evident within 30 seconds of irradiation and maximal damage was reached in less than 10 minutes. Vessel damage was found to depend strongly on lambda. Damage decreased with increasing vessel size. For all D, damage of arterioles was greater than for corresponding venules. CONCLUSIONS: Selection of the correct wavelength is crucial for successful laser therapy of hypervascular lesions and, ideally, should be based on knowledge of vessel diameters for a specific PWS lesion and of optical penetration depths in blood. As a general statement, smaller blood vessels (D = 10-60 microm) should be treated using shorter wavelengths such as 585 nm. To ensure deposition of sufficient laser energy, irradiation at 585 nm, characterized by lower optical penetration depth in blood, may be preferable for PWS therapy.

Animals↗
PubMed1987

Laser modulation of human immune system: inhibition of lymphocyte proliferation by a gallium-arsenide laser at low energy.

Cultured human lymphocytes were subjected to irradiation with a gallium-arsenide laser at energy fluence varying from 2.17 to 651 mJ/cm2, and the cell proliferation was assessed by [3H]thymidine incorporation. Both mitogenic proliferation in response to phytohemagglutinin and spontaneous cell proliferation were markedly inhibited by the laser irradiation at energy fluence as low as 10.85 mJ/cm2. Similarly, the functional response of cells to antigen stimulation in a one-way mixed-lymphocyte reaction was also diminished as a result of laser irradiation. The results indicate that laser irradiation at low energy can interfere with immune system in vitro, and similar modulation could potentially occur in human subjects exposed to laser irradiation in vivo.

Dose-Response Relationship, Radiation↗
PubMed1988

Long-term investigations of laser-assisted microvascular anastomoses with the 1.318-micron Nd:YAG laser.

Laser-assisted microvascular anastomoses can be performed with the most diverse types of laser (Dujovny et al: 4th Annu Gen Sci Meet LANSI, 1986; Godlewski et al: World J Surg 10:329-333, 1986; Gomes et al: Rev Hosp Clin Fac Med Sao Paulo 37:255, 1982; Quigley et al: Laser Surg Med 5:357-367, 1985; Quigley et al: Lancet 1:334, 1985; Quigley et al: Neurosurgery 18(3):292-299, 1986; Jain: J Microsurg 1:436-439, 1980; Jain: Lancet 2:816-817, 1984; Krueger and Almquist: Lasers Surg Med 5:55, 1985; Neblett et al: Neurosurgery 19(6):914-934, 1986; Schober et al: Science 232:1421-1422, 1986; Ulrich et al: 2nd Annu Gen Sci Meet LANSI, 1984; Ulrich and Bock: Optoelectronics in Medicine, Spring-Verlag 418-423, 1986). However, postoperative complications in the form of thromboses and aneurysmatic sacs could be detected in 7-29.8% in longitudinal investigations. By conversion of the beam geometry (1.3 micron Nd:YAG laser, 200 micron light conductor) and use of three concentrically applied 10.0 backstitch sutures in 25 end-to-end anastomoses of the common carotid artery of adult albino rats 0.8-1.2 mm in diameter, early and late complications could be markedly reduced (12%).

Anastomosis, Surgical↗
PubMed1991

Direct comparison of in-vitro and in-vivo Photofrin-II mediated photosensitization using a pulsed KTP pumped dye laser and a continuous wave argon ion pumped dye laser.

A pulsed KTP pumped dye laser (25 kHz repetition rate and 470 nsec pulse width) has been compared to a continuous wave argon ion pumped dye laser as the source of 630 nm light during in-vitro and in-vivo Photofrin-II mediated photosensitization studies. Individual experiments documented the effectiveness of each laser system on a) photosensitizer induced cytotoxicity and induction of stress protein synthesis using Chinese hamster fibroblasts; b) photobleaching of Photofrin-II in aqueous solution; c) Photofrin II mediated photosensitization of normal mouse skin; d) Photofrin II mediated photodynamic therapy of a mouse mammary carcinoma; and e) tumor temperature levels generated during laser exposure. Comparable results were obtained for both laser systems in all experiments.

Animals↗
PubMed2005

Histologic evaluation of the pulsed Nd:YAG laser for laser lipolysis.

BACKGROUND AND OBJECTIVES: Laser lipoplasty with pulsed Nd:YAG laser, widely used in Europe and Latin America, has recently been introduced in Japan and the USA. We report histologic analyses of the effects of the laser on human fat tissue. STUDY DESIGN/MATERIALS AND METHODS: Freshly excised human skin and subcutaneous fat were irradiated with the pulsed Nd:YAG laser (SmartLipo, DEKA, Italy). A 1,064 nm laser at 40 Hz and 150 mJ and 100 microseconds-long pulses were used. Methods of exposure were the same as in the clinical application. In the control group, the specimens were cannulated by the handpiece without irradiation. The tissue was studied by scanning electron microscopy and hematoxylin eosin staining. RESULTS: Scanning electron microscopy after irradiation showed greater destruction of human adipocytes than in the control. Degenerated cell membrane, vaporization, liquefaction, carbonization, and heat-coagulated collagen fibers were observed. CONCLUSIONS: Our study showed that the SmartLipo appeared to be histologically effective for destruction of human fat tissue.

Adipocytes↗
PubMed2003

[Interstitial Nd:YAG laser therapy. Color-Doppler imaging (CDI)-guided laser therapy of hemangiomas and vascular malformations].

BACKGROUND AND OBJECTIVE: Ultrasound-(US-) guided Nd:YAG laser therapy has been reported to be promising among different other options for treatment of hemangiomas and vascular malformations. The concept of CDI-guided interstitial laser therapy is therefore a further development based on the above mentioned therapeutic regime. PATIENTS AND METHODS: We examined 55 patients suffering from vascular lesions of different localization and extent pre-, intra-, and post-operatively using color-Doppler imaging (CDI). All vascular lesions were classified due to their vascularization pattern. As accurate diagnosis was imperative we decided on possible laser treatment depending on the CDI-classification. RESULTS: Intra-operative use of CDI rendered possible fiber-guidance by sonographic navigation and therefore precise treatment of aberrant vessels and well-perfused tumor areas. In 34 cases (62%) we observed complete, in 21 cases (38%) partial regression of vascular lesions. CDI allowed post-operative proof of diminution of tumor vascularization in all cases. CONCLUSIONS: CDI-guided interstitial Nd:YAG laser therapy is a minimally-invasive technique which allows replacement of conventional surgical procedures while achieving good cosmetic and functional results.CDI broadens the therapeutic possibilities in contrast to the former therapeutic concept of US-guided laser therapy due to pre-, intra and post-operative utilization of this imaging technique while significantly diminishing the intra-operative risk for the patient.

Adolescent↗
PubMed2001

[Side-fire laser coagulation of the prostate with the neodymium:YAG-laser. Long-term outcome].

Transurethral laser prostatectomy has been widely used in patients with benign prostatic obstruction (BPO) with good short-term results and an excellent safety profile. We investigated how stable the results of side-firing visual laser coagulation of the prostate are during long-term follow-up to evaluate whether laser prostatectomy can really be an alternative to transurethral resection of the prostate (TURP). Between January 1993 and December 1995 a total of 59 patients underwent visual transurethral side-firing laser coagulation of the prostate (Urolase, Bard Inc., Murray Hill, NJ, USA). The patients were monitored at 1, 3, 6, and 12 months and then reevaluated after a mean of 33 months. As expected, at the 1-year follow-up there was a significant improvement in peak flow rate, post-void residual urine, international prostate symptom score (IPSS) and quality of life index (QoL). After a mean of 33 months, 15% of the patients required reoperation due to persistent BPO. In the remaining patients, peak flow rate and post-void residual urine were stable. However, the QoL index increased during long-term follow-up and no longer differed from the preoperative value after 33 months. The side-firing laser coagulation of the prostate does not seem to be a sufficient therapeutic alternative to TURP in the treatment of BPO.

Aged↗
PubMedDate not supplied

Treatment of small congenital nevocellular naevi using a combination of ultrapulse carbon dioxide laser and Q-switched frequency-doubled Nd-YAG laser.

This report describes treatment combining Ultrapulse CO(2) laser and Q-switched frequency-doubled neodymium:yttrium-aluminum-garnet (Nd-YAG) laser for a number of congenital nevocellular naevi (CNN). The Ultrapulse CO(2) laser removes the superficial component, which contains most of the color, preserving the integrity of the reticular dermis. At a later stage, any residual color is targeted using the Nd-YAG laser. To date, a total of 10 histologically proven CNNs have been treated at the Laser Suite. The median age of the patients was 18 years (range, 13-24 years). All the patients were white females. The patients accepted for treatment had relatively small lesions (mean surface area, 352 mm(2); range, 50-1,092 mm(2)), but the lesions were either cosmetically sensitive or located in an anatomically critical area in which excision could result in a scar that would be unpredictable. The median follow-up period was 24 months. The overall results have been satisfactory, with reduction of color and no significant scarring. The minor textural and pigmentary changes were acceptable to the patients.

Adolescent↗
PubMed2001

[Optimizing laser parameters for intrastromal incision with ultra-short laser pulses].

BACKGROUND: With the assistance of ultrashort laser pulses (ca. 200 fs pulse duration) it is possible to perform precise incisions inside the corneal stroma with a width of a few microns. The advantage of ultrashort pulses is that the required energy of a few microjoules is more than an order of magnitude lower compared with longer pulse durations, i.e. ps or ns pulses. Therefore, the secondary effects, such as thermal and mechanical damage to the surrounding tissue and the amount of radiation reaching the retina, are reduced. This method of intrastromal photodisruption allows a very well defined deposition of energy within the laser focus inside the corneal stroma, accompanied by minimal collateral damage. METHODS: The possibilities of performing intrastromal cuts using fs-laser pulses at a wavelength of 780 nm and pulse durations of 200 fs were studied using a titanium-sapphire laser system. The treated tissue samples were analysed by light and scanning electron microscopy to determine incision quality, reproducibility and achievable accuracy. The mechanical side effects of fs-photodisruption inside the surrounding tissue were analysed by pressure measurements using pyroelectric transducers. CONCLUSION: The thermal and mechanical side-effects of this method are very low and comparable to the effects during excimer treatment. Therefore an application of ultrashort laser pulses in refractive surgery appears to be a feasible alternative.

Animals↗
PubMed2000

Thermal load of laser aperture masks in nonmechanical trephination for penetrating keratoplasty with the Er:YAG laser: comparison between stainless steel and ceramic masks.

PURPOSE: Thermal effects on the laser aperture mask may play a major role in the thermal loading of the cornea during nonmechanical trephination in penetrating keratoplasty. The purpose of this study was to assess the temperature increase on the laser mask using the 2.94-microm Er:YAG laser in order to find suitable parameters for avoidance of thermal damage to the cornea. METHODS: Thermal load measurements were performed on donor (7.5 mm trephination diameter, 0.7 mm thickness, central hole 3.0 mm) and recipient (7.5 mm trephination diameter, 0.7 mm thickness, outer diameter 13.0 mm) aperture masks. The masks were either mounted on a thermal isolator or fixed directly on porcine corneal samples. Temperature increase was measured either under static conditions in the ablation area (setup 1) and at the opposite side of the mask (setup 2) or in the ablation area under dynamic conditions, rotating the whole globe to simulate a constant trephination speed with the mask positioned directly on a porcine cornea (setup 3). We used the NWL Er:YAG solid-state laser in a 1.3-mm free-running spot mode focused on the trephination margin (half of the beam on the mask and half of it on the cornea) with a pulse energy of 200 or 400 mJ and 18CrNi10 stainless steel versus three different types of ceramic masks (silicium carbide, silicium nitrite, aluminum oxide). Temperature was assessed using an infrared pyrometer with automatic data acquisition software for a personal computer. RESULTS: Overall, the temperature rise ranged between 43.6 K (metal donor mask at the trephination area with 400 mJ pulse energy) and 3.3 K (silicium carbide recipient mask at the opposite side of the mask with 200 mJ pulse energy). With all setups and both energy levels, the heating of the metal mask was significantly higher (P<0.02) than the heating of the three types of ceramic masks. The silicium carbide masks revealed the lowest temperature rise. Comparing the three setups, the temperature rise was maximal under static conditions in the ablation area and minimal at the opposite side, with the dynamic setup ranging in between. Temperature rise was significantly greater (P<0.04) in donor masks than in recipient masks for each mask material and both energy levels. CONCLUSION: The physical characteristics of silicium carbide masks seem superior to those of metal masks with regard to minimizing the thermal load of the epithelium or superficial stroma during Er:YAG laser trephination of the cornea for penetrating keratoplasty.

Animals↗
PubMed1988

Laser assisted microvascular anastomosis of arteries and veins: laser tissue welding.

Using a milliwatt CO2 laser, a series of 160 arteries and 105 veins have been anastomosed in Wistar rats. Three stay sutures and a laser tissue welding technique were used. These were compared with a series of conventionally sutured vessels in terms of patency, speed and ease of procedure, and aneurysm formation. Patency rates of successful first time anastomoses are comparable with conventional suturing methods but the aneurysm rate is higher. Laser assisted anastomosis is faster to learn and perform than conventional suturing, but microsurgical skills are still needed. Despite the large number of variables the laser assisted technique has a high success rate, and work to minimise variables and optimise the laser parameters may improve these results.

Anastomosis, Surgical↗
PubMed1990

Laser-induced damage to transparent polymers: chemical effect of short-pulsed (Q-switched) Nd:YAG laser radiation on ophthalmic acrylic biomaterials. II. Study of monomer release from artificial intraocular lenses.

Commercial intraocular lenses and polymer specimens, both poly(methyl methacrylate) (PMMA) and poly(2-hydroxyethyl methacrylate) p(HEMA), were subjected to various levels of irradiation from a Q-switched Nd:YAG laser, and then to extraction and sample-enrichment techniques. The extracts were analysed by capillary gas chromatography. In PMMA samples, residual contents of 0.05-0.89% (wt) MMA were found and it appeared that the laser radiation did not cause a detectable increase of the monomer content. No residual HEMA could be found in p(HEMA) samples before or after laser bombardment. It is concluded that the accidental exposure of lenses to Nd:YAG laser cannot produce a significant release of monomers. Depolymerization induced by laser is a process unlikely to occur at the energy levels used in ophthalmic surgery.

Gas Chromatography-Mass Spectrometry↗
PubMed1995

Chromophore-enhanced laser-tumor tissue photothermal interaction using an 808-nm diode laser.

A diode laser was used to irradiate tumor tissue, with indocyanine green as the chromophore. The 808-nm wavelength radiation falls within the absorption peak of the chromophore (about 780 nm). The preliminary results in this report revealed clear and significant coupling of this laser and indocyanine green in laser-tissue photothermal interaction. The chromophore targeted tissue showed laser damage while peripheral tissues remained intact. Without the chromophore, this laser inflicted no apparent tissue damage in the non-contact mode with irradiance up to 1755 J/cm2.

Animals↗
PubMed2006

Transpupillary argon laser photocoagulation and Nd:YAG laser cystotomy for peripheral iris pigment epithelium cyst.

PURPOSE: To report the use of a combination of transpupillary argon laser photocoagulation and Nd:YAG laser cystotomy in the treatment of peripheral iris pigment epithelium (IPE) cyst. DESIGN: Case report. METHODS: A 23-year-old man presented with a one-month history of blurred vision and pain in the right eye. Slit-lamp biomicroscopy and gonioscopy revealed, in the iridociliary sulcus, a large clear IPE cyst, which was demonstrated by ultrasound biomicroscopy (UBM). A combination of transpupillary photocoagulation to devitalize the epithelial lining and neodymium-doped yttrium aluminum garnet (Nd:YAG) laser cystotomy to drain the cyst was engaged. RESULTS: Laser treatment resulted in vanishing of the cyst and disappearance of the subject symptoms. Two months postoperatively, no evidence existed of the iris pigment cyst regrowth. CONCLUSIONS: The minimal invasiveness of the combination of transpupillary laser photocoagulation and cystotomy yielded a favorable result. This procedure may be an alternative to conservative regimen if IPE cyst is clearly defined and readily seen.

Adult↗