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At least 19 recordsLinked to original sources
PubMed2004

Transmission of Q-switched erbium:YSGG (lambda=2.79 microm) and erbium:YAG (lambda=2.94 microm) laser radiation through germanium oxide and sapphire optical fibres at high pulse energies.

The erbium:YSGG and erbium:YAG lasers are used for tissue ablation in dermatology, dentistry and ophthalmology. The purpose of this study was to compare germanium oxide and sapphire optical fibres for transmission of sufficient Q-switched erbium laser pulse energies for potential use in both soft and hard tissue ablation applications. Fibre transmission studies were conducted with Q-switched (500 ns) Er:YSGG (lambda=2.79 microm) and Er:YAG (lambda=2.94 microm) laser pulses delivered at 3 Hz through 1-m-long, 450-mum germanium oxide and 425-mum sapphire optical fibres. Transmission of free-running (300 micros) Er:YSGG and Er:YAG laser pulses was also conducted for comparison. Each set of measurements was carried out on seven different sapphire or germanium fibres, and the data were then averaged. Fibre attenuation of Q-switched Er:YSGG laser energy measured 1.3+/-0.1 dB/m and 1.0+/-0.2 dB/m for the germanium and sapphire fibres, respectively. Attenuation of Q-switched Er:YAG laser energy measured 0.9+/-0.3 dB/m and 0.6+/-0.2 dB/m, respectively. A maximum Q-switched Er:YSGG pulse energy of 42 mJ (26-30 J/cm(2)) was transmitted through the fibres. However, fibre tip damage was observed at energies exceeding 25 mJ (n=2). Both germanium oxide and sapphire optical fibres transmitted sufficient Q-switched Er:YSGG and Er:YAG laser radiation for use in both soft and hard tissue ablation. This is the first report of germanium and sapphire fibre optic transmission of Q-switched erbium laser energies of 25-42 mJ per pulse.

Aluminum Oxide↗
PubMed1979

Synoviorthesis with erbium-169: a double-blind controlled comparison of erbium-169 with corticosteroid.

Intra-articular injections of erbium--169 citrate and methylprednisolone acetate in hand joints were compared in a randomly selected double-blind trial. The patients included 21 with rheumatoid arthritis and 3 with psoriatic arthritis, and the design was an intrapatient comparison. No difference between joints treated with the radioisotope or steroid was observed in the year following injection.

Arthritis↗
PubMedDate not supplied

Influence of the water content in dental enamel and dentin on ablation with erbium YAG and erbium YSGG lasers.

The theory of the ablation of dental hard tissue with erbium lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The abrupt evaporation of the water is the cause of tissue fragments being blasted out of the tooth structure. The aim of this study is to examine the effect of the water contained in dental hard tissues on the efficiency of ablation. 192 specimens of both bovine dental enamel and bovine dentin are irradiated with an Er:YAG and an Er,Cr:YSGG laser. Half of the specimens are dehydrated beforehand. Irradiation is carried out in subgroups: without water spray and with water spray at flow rates of 0.8 and 3 mls. The ablated volume is determined following histological preparation. Only in dentin, and then only with irradiation with the Er:YAG laser, is the water contained in the tissue found to have a significant influence (p < 0.0001) on the ablated volume. The water content has no effect on the efficiency of laser ablation in any of the other test groups. In contrast, the externally supplied water always has a significant influence on the effectiveness of the ablation process.

Dental Cavity Preparation↗
PubMed2004

Q-switched erbium:YAG laser corneal trephination: thermal damage in corneal stroma and cut regularity of nonmechanical Q-switched erbium:YAG laser corneal trephination for penetrating keratoplasty.

PURPOSE: To assess stromal thermal damage and cut regularity induced by nonmechanical Q-switched Er:YAG laser corneal trephination for penetrating keratoplasty. METHODS: Corneal trephination was performed in 80 enucleated porcine eyes by Q-switched (2.94-microm) Er:YAG laser, along with donor and recipient masks made of metal or ceramic. All combinations of 0.65- or 0.96-mm spot diameter and 45- or 50-mJ/pulse energy setting were used with each of the masks at a 5-Hz repetition rate. Corneas were processed for histologic examinations. Stromal thermal damage was quantified on PAS-stained slides, and cut regularity was assessed semiquantitatively on a scale from 0 (regular) to 3 (highly irregular). Transmission electron microscopy and scanning electron microscopy were performed on selected specimens. RESULTS: The least thermal damage (mean +/- SD = 6.2 +/- 0.7 microm) was found in the donor ceramic group with 50-mJ/pulse energy and 0.65-mm spot diameter, while the best regularity of the cut (1.2 +/- 0.4) was found in the donor ceramic group with 45-mJ pulse energy and 0.65-mm spot diameter. Thermal damage was less pronounced in donor than in recipient corneas (P < 0.01). Smaller spot diameter (0.65 mm) led to less thermal damage (P < 0.01) than the use of a 0.96-mm spot diameter. The differences in thermal damage between ceramic and metal masks were minimal. CONCLUSIONS: After Q-switched Er:YAG laser corneal trephination for nonmechanical penetrating keratoplasty, reproducible high cut regularity and low concomitant thermal damage were observed. This is an encouraging finding in the search for a nonmechanical trephine for penetrating keratoplasty combining high precision and low cost.

Animals↗
PubMed2005

Spectroscopic properties and Judd-Ofelt theory analysis of erbium chelates.

Erbium chelates including tris(acetylacetonato) erbium(III) monohydrate, tris(acetylacetonato)(1,10-phenanthroline) erbium(III) and tris(trifluoroacetylacetonato)(1,10-phenanthroline) erbium(III) are synthesized. Judd-Ofelt theory is employed on basis of the UV-Vis-NIR absorption spectra of erbium chelates dissolved in methanol. Judd-Ofelt parameters of erbium chelates are determined by a least square fitting and dealt with the chemical structure of erbium chelates. Photoluminescence characteristics of erbium chelates are investigated upon excitation at 488 nm by an Ar(+) laser. The qualitative correlation of Judd-Ofelt parameters with photoluminescence properties for erbium chelates is also discussed. It is found that larger Omega(6) value for erbium chelate is and larger photoluminescence intensity at 1.54 microm is, and Omega(2) value should contribute to the photoluminescence full width at half maximum (FWHM) at 1.54 microm. The changes of Judd-Ofelt parameters result from the introduction of the second ligand phenathroline or the substitution of electron-drawing group CF(3) in beta-diketone for erbium chelates.

Chelating Agents↗
PubMed2005

Site-selective spectroscopy of the solid-state defect chemistry in erbium-doped barium titanate.

Erbium-doped barium titanate crystals were studied by laser-induced fluorescence spectroscopy. Thirteen spectroscopically distinct erbium ion sites were found. The relative concentrations of the different sites changed as a function of the crystal and its preparation and treatment. One major site was present in all crystals. The site distribution was changed either by growing codoped crystals with donor (La3+) and acceptor (Sc3+) ions or by changing the temperature and partial pressure of the oxygen in the annealing atmosphere. Equilibrium calculations were done to simulate the defect distributions that result from the charge compensation of the erbium ions. Comparison with the observed dependence of the site spectral intensities indicated that the erbium enters the lattice on barium sites. We assigned the dominant site to an erbium ion on a barium site that is locally compensated by a barium vacancy, whereas the other lower-intensity sites corresponded to erbium ions that are locally compensated by an electron and a more complex center of an erbium, a barium vacancy, and a hole. The spectra of one sample showed that its defects were different and were characteristic of a sample that had not equilibrated. The new sites in this sample were assigned to erbium entering the lattice on a titanium site, which was then locally compensated by an oxygen vacancy or a hole. Heating equilibrated the sample and changed the erbium to a barium site.

Journal Article↗
PubMed2002

Use of a novel erbium laser in a Yucatan minipig: a study of residual thermal damage, ablation, and wound healing as a function of pulse duration.

BACKGROUND AND OBJECTIVE: Theoretical models show that varying pulse duration influences residual thermal damage in erbium YAG skin resurfacing. Accordingly, our objective was to compare residual thermal damage, ablation, tissue shrinkage, and wound healing between a variable pulsewidth erbium YAG laser and a popular CO2 resurfacing laser. STUDY DESIGN/MATERIALS AND METHODS: The erbium laser delivered a typical ablative pulse (250 microseconds), followed by a heating pulse of variable duration. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of one Yucatan pig were irradiated. Eight sites were treated per group. Biopsies were performed just after treatment and 1, 3, 7, 21, and 60 days postoperatively. RESULTS: Just after irradiation, gross examination of "cold" (without a coagulation pulse) erbium sites showed a reddish papillary dermis consistent with conventional erbium laser ablation. Two and three pass CO2 sites showed uniform surface yellowing. The longer pulsewidth ("hot") erbium groups showed only slight surface yellowing. Biopsies showed immediate thermal damage that increased with erbium pulse duration; however, actual residual thermal damage (RTD) was sometimes less than that predicted by the laser control panel. All wounds healed uneventfully by 14 days. CONCLUSIONS: An erbium laser with a variable macropulse pulsewidth was capable of achieving RTD of up to 80 mum. Even greater RTD depths may be obtainable with future manipulations of fluence and pulse duration.

Animals↗
PubMed2001

Histopathologic and morphometric evaluation of the skin abnormalities induced by erbium:YAG and carbon dioxide lasers in 10 patients.

In the 1960s, carbon dioxide (CO2) laser therapy started to be applied to eliminate wrinkles, actinic scars, and acne because of its capacity of induce intracellular water vaporization. However, recent studies have shown the efficacy of the erbium laser in removing delicate and moderate scars. Furthermore, the postoperative lesions induced by the erbium laser seem to resolve faster and with less erythematous pattern compared with lesions induced by the CO2 laser. The purpose of this study was to determine the immediate pathologic alterations caused by single applications of CO2 and erbium lasers and their association in human skin shreds. Ten white female patients aged 30 to 63 years underwent rhytidectomy, and their respective shreds, which were prepared for excision, were tattooed with the CO2 laser, the erbium laser, or a combination of both in random order and number of applications, before final removal. This project was approved by the local ethical committee. After surgical removal, these tattooed shreds were fixed in 10% buffered formalin and submitted to histopathologic analysis. Morphometric studies demonstrated the normal skin thickness and thickness of the laser-treated area, and their subtraction resulted in the ablation damage values. Residual thermal damage corresponded to the thickness of the affected skin from the most superficial layer of tissue in the laser-treated area down to the deepest dermal area with basophilic degeneration of collagen fibers. Our results showed that two CO2 applications resulted in greater ablation and residual thermal damage when compared with only one CO2 application. The same was true in comparisons of one and two applications of the erbium laser. Both results were statistically significant (p < 0.05). When one isolated erbium and one isolated CO2 application were compared, ablation damage was greater in the former group, although with no statistical significance. One CO2 plus one erbium application compared with one isolated CO2 application showed similar ablation damage but greater residual thermal damage in the latter group (p < 0.05). These observations might contribute to our understanding of the lesions caused in the human skin by erbium and CO2 lasers and eventually help determine the ideal laser combination for the appropriate surgical treatment.

Adult↗
PubMed1999

Synthesis, Structure, and Molecular Orbital Studies of Yttrium, Erbium, and Lutetium Complexes Bearing eta(2)-Pyrazolato Ligands: Development of a New Class of Precursors for Doping Semiconductors.

Treatment of yttrium metal with bis(pentafluorophenyl)mercury (1.5 equiv), 3,5-di-tert-butylpyrazole (3 equiv), and pyridine (2 equiv) in toluene at ambient temperature for 120 h afforded tris(3,5-di-tert-butylpyrazolato)bis(pyridine)yttrium(III) (33%). In an analogous procedure, the reaction of erbium metal with 3,5-dialkylpyrazole (alkyl = methyl or tert-butyl), bis(pentafluorophenyl)mercury, and a neutral nitrogen donor (4-tert-butylpyridine, pyridine, n-butylimidazole, or 3,5-di-tert-butylpyrazole) yielded tris(3,5-di-tert-butylpyrazolato)bis(4-tert-butylpyridine)erbium(III) (63%), tris(3,5-di-tert-butylpyrazolato)bis(pyridine)erbium(III) (88%), tris(3,5-di-tert-butylpyrazolato)bis(n-butylimidazole)erbium(III) (48%), tris(3,5-dimethylpyrazolato)bis(4-tert-butylpyridine)erbium(III) (50%), and tris(3,5-di-tert-butylpyrazolato)(3,5-di-tert-butylpyrazole)erbium(III) (59%), respectively. Treatment of tris(cyclopentadienyl)lutetium(III) or tris(cyclopentadienyl)erbium(III) with 3,5-di-tert-butylpyrazole (3 equiv) and 4-tert-butylpyridine (2 equiv) in toluene at ambient temperature for 24 h afforded tris(3,5-di-tert-butylpyrazolato)bis(4-tert-butylpyridine)lutetium(III) (83%) and tris(3,5-di-tert-butylpyrazolato)bis(4-tert-butylpyridine)erbium(III) (41%), respectively. The X-ray crystal structures of all new complexes were determined. The X-ray structure analyses revealed seven- and eight-coordinate lanthanide complexes with all-nitrogen coordination spheres and eta(2)-pyrazolato ligands. Molecular orbital calculations were carried out on dichloro(pyrazolato)diammineyttrium(III). The calculations demonstrate that eta(2)-bonding of the pyrazolato ligand is favored over the eta(1)-bonding mode and give insight into the bonding between yttrium and the pyrazolato ligands. Complexes bearing 3,5-di-tert-butylpyrazolato ligands can be obtained in a high state of purity and sublime without decomposition (150 degrees C, 0.1 mmHg). Application of these complexes as source compounds for chemical vapor deposition processes is discussed.

Journal Article↗
PubMed2003

Side effects and complications of variable-pulsed erbium:yttrium-aluminum-garnet laser skin resurfacing: extended experience with 50 patients.

Recent advances in technology have provided laser surgeons with new options for cutaneous laser resurfacing. Despite its popularity, there is limited information on the short-term and long-term side effects and complications of variable-pulsed erbium:yttrium-aluminum-garnet (erbium:YAG) laser skin resurfacing. The purpose of this study was to prospectively evaluate postoperative wound healing, side effects, and complications of multiple-pass, variable-pulsed erbium:YAG laser skin resurfacing for facial photodamage, rhytides, and atrophic scarring. Fifty consecutive patients with facial photodamage, rhytides, or atrophic scarring were treated with a variable-pulsed erbium:YAG laser. Side effects and complications relating to postoperative healing, erythema, and pigmentary changes were tabulated. Patients were evaluated at postoperative days 3 through 7 and at 1, 3, 6, and 12 months after laser skin resurfacing. The average time for reepithelialization was 5.1 days. Prolonged erythema (>1 month) was observed in three patients (6 percent). Transient hyperpigmentation occurred in 20 patients (40 percent), with an average duration of 10.4 weeks. No cases of hypopigmentation or scarring were seen. In summary, a variable-pulsed erbium:YAG laser can safely be used for the treatment of facial photodamage, rhytides, and atrophic scarring. Although more postoperative erythema is seen after variable-pulsed erbium:YAG laser treatment than is usually produced with a short-pulsed erbium:YAG system, the side-effect profile and recovery period after variable-pulsed erbium:YAG laser skin resurfacing still are more favorable than after multiple-pass carbon dioxide laser skin resurfacing.

Adult↗
PubMed1999

Advantages and dangers of erbium laser application in stapedotomy.

Among different types of lasers, the erbium laser exhibits particularly favourable characteristics for ear surgery. Experiments with application of erbium laser pulses to the isolated stapes connected to an inner ear model confirmed that there was virtually no thermal effect to the inner ear liquid and that the border damage zone on the stapes footplate perforation did not exceed 5-10 microm. Erbium laser pulses, however, produce pressure waves due to the explosive ablation of tissue. Pulses of 10 to 17 J/cm2 producing pressure waves between 140 and 160 dB appear to be a limit for clinical application. With these criteria, an in-house built erbium YAG laser with a fiberoptic delivery device was used in 15 patients for stapedotomy. A special microhandpiece, where a zirconium fluoride fiber was connected to a quartz tip, was developed. In addition, three patients had stapedotomy with a commercially available Zeiss (Opmi TwinER) microscope equipped with a micromanipulator-operated erbium laser beam. One year after surgery, the air-bone gap was closed in all patients to within 20 dB between 0.5 and 3 kHz with only minor permanent bone conduction threshold losses (< 20 dB). However, we observed an immediate postoperative middle and high frequency loss of up to 75 dB on bone conduction threshold measurements 2 h after surgery, suggesting an acoustic traumatization by the erbium laser. This threshold shift recovered close to preoperative values within 6 h. These observations prompted us to discontinue the clinical use of erbium laser for stapedotomy until the problem of temporary acoustic traumatization is resolved.

Adult↗
PubMed1999

Pulsed carbon dioxide and long pulse 10-ms erbium-YAG laser resurfacing: a comparative clinical and histologic study.

BACKGROUND: The recent introduction of pulsed erbium-YAG laser technology has been accompanied by relatively few clinical studies with widely varying claims regarding postoperative healing, clinical side-effects and efficacy. We evaluated a new long (10 ms) pulsed erbium-YAG laser in order to determine safety and clinical efficacy in comparison with a pulsed carbon dioxide laser. OBJECTIVE: Our objective was to comparatively evaluate a pulsed CO2 and long-pulsed erbium-YAG laser with regard to clinical side-effects, postoperative healing and efficacy in the reduction of rhytids. METHODS: Bilateral periocular or perioral sites were treated using a pulsed CO2 (UltraPulse) laser on one side and long-pulsed erbium-YAG laser (CO3) on the opposite side. Histologic specimens were also studied in order to compare tissue effects of both lasers. RESULTS: Results showed equivalent postoperative healing and lack of complications. In addition, the long-pulsed erbium-YAG laser showed significant efficacy in the treatment of mild and moderate rhytids. CONCLUSION: The long-pulsed (10 ms) erbium-YAG laser appears to be of significant benefit in the treatment of facial rhytids. Tissue studies show a greater degree of thermal damage in the dermis when compared to traditional 350 microseconds erbium-YAG lasers which may underlie the beneficial effects of this laser in the treatment of aging skin.

Adult↗
PubMed1999

Clinical and histologic evaluation of six erbium:YAG lasers for cutaneous resurfacing.

BACKGROUND: Several erbium:YAG lasers are currently available for cutaneous laser resurfacing. Although different laser systems are purported to produce equivalent laser energies to produce similar laser-tissue interactions, no comparative clinical or histologic studies have been performed to objectively demonstrate their relative efficacies. OBJECTIVE: The purpose of the present study was to examine the in vivo clinical and histopathologic effects of six different erbium:YAG resurfacing lasers. METHODS: A blinded, prospective study using six different erbium lasers (Candela, Continuum Biomedical, HGM, MDLT, SEO, Sharplan/ESC) was performed. The facial halves of 12 patients were randomly resurfaced with one of the six laser systems by using an identical laser technique at 5.0 J/cm2. Intraoperative skin biopsies were obtained after each of three laser passes in two patients for blinded histologic determination of tissue ablation level and presence of residual thermal damage. Clinical assessments of reepithelialization rates, severity and duration of erythema, side effects, and degree of clinical improvement were made at 0.5, 1, 2, 4, 12, 26, and 52 weeks postoperatively. RESULTS: Irrespective of the erbium laser system used, complete reepithelialization typically occurred at 0.5 weeks and resolution of erythema was noted within 1-2 weeks postoperatively. A mean clinical improvement of 50% was observed, with photodamaged skin showing greater improvement than scarred skin. The most common postoperative side effect was hyperpigmentation, with all affected patients having either darker skin tones or preceding dermal inflammation. Three laser passes were needed to effect total epidermal ablation when using any one of the erbium:YAG systems. CONCLUSIONS: Equivalent clinical and histologic results were seen after each of the six erbium:YAG lasers studied. Erbium:YAG laser resurfacing can be used to significantly improve mild cutaneous photodamage and atrophic scars.

Adult↗
PubMed1999

Erbium laser resurfacing: current concepts.

Laser skin resurfacing has enjoyed great popularity in recent years with the introduction of computerized, pulsed carbon dioxide lasers. However, the morbidity and side effects of carbon dioxide lasers have stimulated a search for alternative methods of skin remodeling. The erbium:YAG laser can be successfully used for skin resurfacing, with lower morbidity than the carbon dioxide laser. In a series of 625 patients who had erbium:YAG resurfacing, the following conclusions were reached. (1) Long-term (> 6 months) improvement in wrinkles and acne scars required total fluences exceeding 20 J/cm2. Periocular wrinkles required total fluences of between 20 and 40 J/cm2, depending on the depth of the wrinkles and skin thickness. Perioral rhytids required total fluences of between 40 and 80 J/cm2, whereas the cheeks and forehead required total fluences of 30 to 60 J/cm2. (2) Deeper wrinkles were best treated with a combination of erbium and carbon dioxide lasers, which minimized the bleeding that occurs with deeper erbium resurfacing. The simultaneous combined erbium with carbon dioxide laser was particularly advantageous. (3) Complications were relatively uncommon using the scanning erbium laser, and most adverse effects occurred early in the series. Scarring occurred in 5 of the 625 patients (0.8 percent) and mostly resolved with intralesional steroids. Hyperpigmentation occurred in 21 of the 625 patients (3.4 percent) and was temporary in nature. Hypopigmentation, which became evident after 6 months, occurred in 25 of the 625 patients (4.0 percent) but was mild and not a significant cosmetic problem, except in one patient who developed scarring on the neck. Hypopigmentation seemed to be related to the depth of resurfacing. Four of the 625 patients (0.6 percent) developed temporary scleral show, but no patients had permanent ectropion. Eight of the 625 (1.3 percent) developed synechiae under the lower eyelid, which required minor correction.

Acne Vulgaris↗
PubMed2005

[Synthesis, characterization and NIR luminescence properties of erbium organic complexes].

Several erbium organic complexes, hydrated erbium binary complexes with acetylacetone (AcAc) or dibenzoylmethane (DBM), erbium ternary complexes derived from 1,10-phenanthroline (Phen) with acetylacetone (AcAc), dibenzoylmethane (DBM) or trifluoroacetylacetone (TFA), were synthesized and identified by elemental analysis. The UV-Vis absorption and FTIR spectra measurements have been employed for all the erbium complexes. Near infrared (NIR) photoluminescence properties, such as luminescence intensity and effective bandwidth, of the erbium complexes were also studied. As a result, the erbium ternary complex with AcAc and Phen exhibits the most excellent luminescence properties among those investigated complexes.

Chalcones↗
PubMedDate not supplied

Achieving superior resurfacing results with the erbium:YAG laser.

Laser skin resurfacing has become increasingly popular. The carbon dioxide (CO2) laser seemingly remains the most commonly used laser modality for skin resurfacing. Many surgeons still promote the CO2 laser as being superior to the erbium:YAG laser, particularly for individuals with deeper lines. However, further experience with the erbium:YAG laser has shown the converse to be true. The erbium:YAG laser can be used to treat deep rhytids successfully, many times achieving results superior to those seen with the CO2 laser, particularly in the perioral region. The theory behind this relates to the 10-fold greater absorption of the erbium:YAG wavelength by water. The greater absorption produces more efficient vaporization, even at low fluences, with greatly reduced adjacent thermal injury. Ablation can be carried to deeper levels of the dermis than is consistently safe with the CO2 laser. Deliverance of total fluences in the range of 100 to 150 J/cm2, or more, produces a marked reduction or elimination of deeper rhytids. Clinically, experience with more than 300 cases indicates collagen remodeling occurs to a similar degree with the erbium:YAG laser as with the CO2 laser, as improvement in rhytids can be seen for 2 to 3 months after surgery. It would appear that superior results can be obtained without the "heat effect" of the CO2 laser. The erbium:YAG laser is capable of achieving superior resurfacing results, while offering many advantages to the patient, eg, reduced anesthetic requirements, shorter healing time, reduced erythema, less risk of pigmentary change, and more flexibility for resurfacing the skin off of the face.

Humans↗
PubMed2002

Erbium: YAG laser lithotripsy mechanism.

PURPOSE: We tested the hypothesis that the mechanism of long pulse erbium:YAG laser lithotripsy is photothermal. MATERIALS AND METHODS: Human urinary calculi were placed in deionized water and irradiated with erbium:YAG laser energy delivered through a sapphire optical fiber. Erbium:YAG bubble dynamics were visualized with Schlieren flash photography and correlated to acoustic emissions measured by a polyvinylidene fluoride needle hydrophone. The sapphire fiber was placed either parallel or perpendicular to the calculus surface to assess the contribution of acoustic transients to fragmentation. Stones were irradiated using desiccated stone irradiated in air, hydrated stone irradiated in air and hydrated stone irradiated in water. Ablation crater sizes were compared. Uric acid stones were irradiated in water and the water was assayed for cyanide. RESULTS: During the early phase of vapor bubble expansion, acoustic transients had minimal effects on calculus fragmentation. Fragmentation occurred due to direct absorption of laser energy transmitted to the calculus through the vapor channel between the sapphire fiber tip and calculus. The forward axial expansion of the bubble occurred more rapidly than the radial expansion. A parallel oriented fiber on the calculus surface produced no fragmentation but generated larger amplitude acoustic transients compared to perpendicular orientation. In perpendicular orientation the erbium:YAG laser did not generate any collapse acoustic waves but fragmentation occurred. Crater width was greatest for desiccated stones irradiated in air (p <0.03). Cyanide production increased as erbium:YAG irradiation of uric acid calculi increased, (r2 = 0.98). CONCLUSIONS: The erbium:YAG laser fragments stones through a photothermal mechanism.

Humans↗