Search

An efficient high-peak-power Ho:YAG hybrid laser resonantly pumped by a 20 W linearly polarized Tm:fiber laser at the wavelength of 1908 nm was developed. At room temperature a maximum continuous output power of 10.7 W with a slope efficiency of over 55% with respect to the incident pump power was achieved. In Q-switching regime an acousto-optic modulators were applied. The research was conducted for normal and Brewster's angle Q-switches respectively. In CW pumping regime the repetition rate was changed from 500 Hz to 5000 Hz. For the best case, for 5 kHz repetition rate, pulses of 1.6 mJ energy and 123 kW peak-power were achieved at the wavelength of 2090.2 nm with an M 2 ≈ 1.6.

Objective: To observe the Effect of Oral Mucoid Cyst Treated by Ho:YAG Laser. Methods: The patients suffering from oral mucoid cyst were treated by Ho:YAG laser, which energy per pulse is 0.5j, pulse per second 5~15Hz, average power 2.5~7.5w. Result: Among all the patients were cured for one time. Conclusion: The technique of treatment of oral mucoid cyst with Ho:YAG laser is an effect and safe thearapeutics with the characteristics of excellent homeostasis, improved visualization, minimal thermal damage to surrounding tissue, shorter period of recovery and easy to operate. The total effect of Ho:YAG laser is better than CO 2 laser and Nd:YAG laser.

Objective: To observe the effect of Ho:YAG laser in treatment of urethra cauncle. Methods: The patients suffering from urethra cauncle were treated by Ho:YAG laser, the energy of per pulse is 0.5J. The frequency of pulse is 5~15Hz, and the average power of the laser is 2.5~7.5W. Results: Among the patients 188 cases of urethra cauncle were only cured for one time, twice for 12 cases. No stricture on the peristome of urethra or urethrovaginal fistula was observed. Conclusions: The technique of treatment of urethra cauncle with Ho:YAG laser is an effect and safe therapeutics with the merit of excellent homeostasis, improved visualization, minimal thermal damage to surrounding tissue, shorter period of recovery and easy to operate. It is better than CO 2 laser and Nd:YAG laser.

Objective: The purpose of this study to evaluate the effectiveness of Ho: YAG laser irradiation in treatment of condylomata acuminata. Methods: 1025 patients of condylomata acuminata, in which the lesions of 620 patients were interior of different lacuna, the lesions in 79 patients were huge (the diameter of lesion is over than 5cm), and 26 patients were pregnant, were treated with Ho:YAG laser (0.5-0.8J/pulse, 5-15 pulses/sec) to melt all the lesions. Results: All lesions in 1025 patients were removed after one laser treatment. The recrudescent and regenerative lesions could be removed completely after repeated treatment. No scarring and stricture on the peristome of the urethra was observed. No abortion, premature delivery and other syndrome were occurred among the total 26 pregnant patients. Conclusion: The technique of treatment of condylomata acuminata with Ho:YAG laser is an effective and safe therapeutics with the characteristic of better function of the homeostasis, shorter period of the concrescence and easy to operate.

The Ho:YAG laser use in the different superficial disease and intracavity disease through endoscopy was introduced. The safe parameters of Ho:YAG laser use in the clinical was given out.

We reported 25 cases of cerebellopontine angle (CPA) tumor operation with Ho:YAG laser assistance during the operative procedure. We analysed the surgical effects of Ho:YAG lase r, compare it with CO 2 A Nd:YAG A argon laser, and illustrated its features and parameters. We think that Ho:YAG laser can be used to ablate and vaporize the tumor efficiently in the operation of the CPA tumo rs whose vascular supply is abundant and the texture is very tough. It can be used to reduce the bleeding and cooperate to incise tumor in the operation and improve the curable effect of the surgery. Keywords: Ho: YAG laser cerebellopontine angle tumor 1. INTRODUCTION The operation of CPA tumor is always a challenge to the neurosurgeon not for the total resection of the tumor, but the reservation of the nerve. In recent year, successful application of laser in neurosurgery has been reported. We also report our experience in a series of 25 patients that applied Ho:YAG laser cooperated the operation of CPA tumor from April 1994 through December 2002.

Background and Objective: To evaluate the efficiency of transmyocardial revascularization with Ho:YAG laser and find out adequate physical parameters of the laser. Materials and Methods: 10 dogs were studied. All the samples were divided into two groups: the laser group (5 dogs) and the control group (5 dogs). Acute myocardial ischemia was induced in all the samples, and transmyocardial laser revascularization (TMLR) was only done in the laser group. We compared the difference of improvement in myocardial perfusion between the two groups with single photon emission computed tomograph (SPECT) and observed the patency of the laser channels and heat injures in the tissue adjacent to the channels with light- and electro-scope. Results: After 4 weeks, the recovery of myocardial perfusion was significantly faster in the laser group than in the control group through SPECT (P

Stenotic, collapsed, and flow-restricted tracheal airways may result from blunt trauma, chronic infection, and the prolonged endotracheal intubation. This pilot investigation characterizes the degree of shape change produced by Ho:YAG laser (λ=2.12 μm) irradiation of rabbit and pig trachea tissue as a function of laser dosimetry and application protocol. Force displacement curves were generated using fresh lagomorph and porcine tracheal cartilage rings secured in a modified single beam cantilever geometry. These specimens were then irradiated for varying amounts of time and power with the objective of straightening these curved specimens. The degree of shape change was documented photographically. Force and surface temperature were monitored. Confocal microscopy was then used in combination a vital staine (“live-dead assay”) to determine the level of viability of straightened cartilage for selected exposure time-power pairs. Laser Cartilage Reshaping of the trachea may provide a new method to treat severe tracheal injuries without the need for classic open surgical techniques. This pilot investigation is the first step toward demonstrating the feasibility of this technique. Long-term, the design of stents combined with laser irradiation may provide a means to alter tracheal shape.

Introduction . A considerable confusion exists in literature regarding the comparison between the employ of the laser and TUR for the treatment of Superficial Bladder Cancer (SBC) in terms of tumour recurrences (number, progression of stage and grade, place and time of them) and the economic costs. For this reason we have analysed the two procedures by a retrospective study to evaluate if the laser treatment had same advantages on the TUR which is still now considered the gold standard treatment. Materials and Methods . We examined two groups of 50 elderly patients with DBC, high incidence of comorbilities and anaesthesiological risk, who were treated by TUR or Ho. Yag laser. We considered for teh resected tumours: stage, grade, size, multiplicity, history. Of the recurrences were analysed: number, place, time of appearance, grade and stage. Besides the time of surgical procedure, the complication rate, the catheterization time and the hospital stay were evaluated. Results . There was not a clear difference between laser and TUR about the recurrences for: number (30% and 36%), progressoin of stage and grade, place and time of appearance. An important results it was that at parity of surgical time in the laser group we had: 50% less of complications, 75% of the patients removed the catheter within 24hs with a postoperative stay of 24-48 hs instead of 4% and 40% in the TUR group. Conclusions . We conclude that the use of the Ho: YAG laser is actually the most advantageous method to treat the elderly with comorbilities and affect by little relapsing and low grade SBC for the low complication rate, reduction of the catheritization time, the hospital stay and the economic costs. These results point out that the Ho:Yag laser is an interesting technology to treat the elderly with comorbilities and this characteristic is still more important if we consider that for the ageing of the population we are moving towards an increase of the elderly urological pathology.

Among other applications, Q-switched, single-mode and high energy Ho:YAG lasers are useful tools in temperature- jump experiments designed for biophysical research. But if pulse energies of 200 J at one microsecond pulse widths or shorter are to be generated in a single oscillator, the damage threshold of the optical coatings is likely to be exceeded. Experiments with an oscillator/amplifier system show that the saturation fluence of Cr,Tm,Ho:YAG amounts to 2.3J/cm2 and that a small signal gain coefficient of 0.15/cm can be obtained at moderate pump densities. This suggests the use of extracavity ampli cation if high power holmium pulses are required.

Among tumors of urinary system, the morbidity of bladder cancer is the first one. It is multiple, also has high risk of regeneration. The paper reports that 679 bladder tumors in 108 patients had treated for 284 times by pulsed HO:YAG laser from July 1994-June 1997.

10 patients with vocal cord polyps treated by the Ho:YAG laser were reported with cure rate of 100 percent and no recurrence. The Ho:YAG laser vaporized the polyps tissue with non bleeding during operation, and mild postoperatively in vocal cord. The hoarseness caused by vocal cord edema would disappeared within one week. During one year of our follow-up, no residual or recurrent cases were found. All patients acquired hormonal voice quality.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A total of 420 cases of OSAS patients underwent laser- assisted uvlopalatoplasty (LAUP) with CO2 and Ho:YAG laser, the follow-up period range 1-12 months in 360 cases. According to our overall response rate, total improvements in 60 percent of patients, significant improvement in 100 percent of patients. Except minor bleeding, no serious complications were observed, so LAUP should be considered as an alternative to UPPP.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Intranasal Holmium:YAG laser dacryocystorhinostomy after failed external dacryocystorhinostomy were successfully performed in 6 patients. The inner wall of lacrymal sac is identified by the illumination of a fine fibroptic probe which is passed through the upper canaliculus and directed medially into the obstructed sac. The most bright spot as seen intranasally is marked as a target for laser penetration, using O.5-1J, 5-15w, 10-15 pulses/second. Through 400um quartz fiber delivery depending upon the consistency of the tissue. The new opening about 6mm in diameter is made with relative ease from inside of nasal cavity as the opening is only 40 42mm from the nostril. A silicone rod of 2 loops or 3 loops is introduced retrogradely into the lacrymal passage as a stent which should stay for 4 months or longer. Among the 6 patients, 5 cases were successful. The follow up period were 4-17 months after removal of silicone rods. One case was failed as the silicone rod was accidentally broken at 5 weeks after operation. The advantages of this operation are: avoidance of skin incision, deep sutures, bleeding and scarring.

The results of a closed loop thermal feedback controlled laser-assisted tissue welding study in vivo are reported. A series of experiments was carried out to study and compare the weld strength and healing response of sutured and laser welded rat enterotomies with and without temperature feedback control (TFC) using a cryogenically cooled Ho:YAG laser. Although assignment of animals to three groups (control sutured, laser welded with and without TFC) and four observation periods (1, 3, 7, and 21 days) was randomized, several laser welded enterotomies without TFC had complications resulting in death of the animals. Those experiments were repeated. From the failure rates encountered, it is shown that TFC improves the quality of laser-assisted enterotomy closures.

Among the commonly available surgical lasers, the CO2 laser has acquired a unique role in oral, laryngeal, and tracheo-bronchial surgery. Other wavelengths, and in particular, frequency doubled Nd:YAG laser, the KTP-532 is also gaining ground, offering the advantage of the fiber transmissivity. A number of new lasers are being introduced. The question of their usefulness in the field of otolaryngology can best be answered by systematic study of the peculiar requirement of the surgical procedure, the tissue interactions of any particular wavelength/s, the ease with which the beam can be targeted, and so on.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Among the commonly available surgical lasers, the CO2 laser has acquired a unique role in oral, laryngeal and tracheo-bronchial surgery. Other wavelengths, and in particular, frequency doubled Nd:YAG laser, the KTP-532 is also gaining ground, offering the advantage of the fiber transmissivity. A number of new lasers are being introduced. The question of their usefulness in the application for nasal surgery can best be answered by systematic study of the peculiar requirement of the surgical procedure, the tissue interactions of any particular wavelength/s, the ease with which the beam can be targeted and so on.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This study evaluated the effect of the Ho:YAG laser operating at a wavelength of 2.1 micrometers and a repetition rate of 2 Hz on a human scleral tissue. The effects were assessed in terms of the ablation rate (micrometers /pulse) and the thermal damage (micrometers ) induced. The results were compared to those found from porcine scleral ablation. Data indicate that for the pulsed Ho:YAG laser, the ablation rate of scleral tissue increases linearly with laser fluence. The ablation rates are about 40% lower for the human scleral tissue than for the porcine scleral tissue at the same fluences. Data indicate that the mean Ho:YAG laser induced thermal damage is not significantly affected by varying the fluence.

The effects of the Ho:YAG (2.13 micrometers ) laser on rabbit scleral tissue ablation were determined. Over a period of 12 months the status of the drain hole was monitored. A 3 mm incision was made on 26 rabbits through the conjunctiva and the laser probe was advanced and applied under it. A fluence of 255 J/cm2 was used to perforate the sclera with a pulse duration of 300 microsecond(s) ec full width at half maximum. Results of this study show that this laser thermal sclerostomy procedure provided a patent hole in 6 of 8 (75%) eyes at 3 months, 11 of 15 (73%) eyes at 6 months, and 3 of 3 at 12 months. No postoperative inflammation, hypotony or subsequent scar formation was observed in any of the rabbits.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Diode-pumped operating scheme for Ho:YAG laserB.M.Antipenko, A.A.NikitichevAll-Union Research Center "S.I.Vavilov State Optical Institute" 199034 St.Petersburg, RussiaIn this paper we shall touch upon a problem of output power scale up of diode-pumped Ho-laser. Raising outputpower we are forced to use both a large volume of active medium and compulsory cooling. There is the expression

The Ho:YAG laser is used to perform percutaneous lumbar discectomy in swine to evaluate the procedure as a potential clinical tool.