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At least 469 records · Page 26Linked to original sources
PubMed1986

The microcirculation in neodymium-YAG laser irradiated and in electrocoagulated urinary bladder tumors evaluated with laser Doppler flowmetry.

Neodymium-YAG laser irradiation is a relatively new therapeutic modality for the treatment of urinary bladder tumors which is suggested to produce an instantaneous arrest of the blood circulation and a homogeneous coagulation of the tumor tissue. Utilizing the laser Doppler flowmetry principle the microcirculatory changes in laser irradiated tumors were compared to the changes in tumors coagulated with diathermy. In laser treated tumors the blood cell flux decreased to near baseline levels throughout coagulated area. Vascular stasis was demonstrated in the erythematous zone encircling the necrosis. In tumors coagulated with diathermy a corresponding constant decrease in blood cell flux could not be demonstrated. Thus the neodymium-YAG laser irradiation seems preferable to electrocoagulation in the treatment of urinary bladder tumors as more complete and homogeneous arrest of the blood circulation in the treated area is achieved.

Electrocoagulation↗
PubMedDate not supplied

[Laser mass spectrometric analysis of biomedical samples using basic and second harmonics of yttrium-aluminum-garnet laser].

Laser mass spectrometric analysis of a biomedical sample was made on exposure to laser radiation at lambda 2 = 532 nm. The parameters of laser radiation and mass spectra were comparatively analyzed by using the basic and second harmonics of aluminum-yttrium-garnet-based laser. The sensitivity of laser mass spectrometry of biomedical samples is increased.

Animals↗
PubMed1986

A comparison between laser excisional conization and laser vaporization for the treatment of cervical intraepithelial neoplasia.

One hundred twenty patients with cervical intraepithelial neoplasia who were treated by laser excisional conization were compared with a group of 100 women who had similar diagnoses and were treated by laser vaporization. Every operation in the series was performed in the outpatient surgical unit or in the office. In two thirds of the cases the procedures were carried out with the patients under local anesthesia. The parameters studied included time required to perform the procedure, immediate and delayed bleeding, postlaser stenosis, healing time, patient discomfort, persistence or recurrence of disease, and risk of invasion. The results of this study revealed few disadvantages to performing a laser excisional procedure. Immediate and delayed complications were less frequent with laser excisional conization. The time required to perform an excisional conization was on the average only 4 minutes longer than that for a vaporization. Most significantly, the laser excisional cone provides a large and excellent specimen for the pathologist to review.

Constriction, Pathologic↗
PubMed2002

Lasers and laser-tissue interaction.

Light produced by a laser differs from incandescent light in that it is monochromatic, coherent, and intense; and it is these properties that allow lasers to be used as such unique tools in biomedical research and patient care. The effect of a laser beam on tissue is dependent on the optical and mechanical properties of the tissue, and the wavelength, power parameters, and time domains of the laser exposure. Understanding these principles is not only important for the selection of an appropriate laser system for a specific application, but also is essential for that application to be successful.

Animals↗
PubMed2002

Diode laser and endoscopic laser surgery.

Two functionally important differences exist between the diode laser and the carbon dioxide (CO2) laser (used more commonly in small animal surgery). Diode laser energy is delivered through a quartz fiber instead of being reflected through an articulated arm or waveguide. Quartz fibers are generally more flexible and resilient than waveguides and can be inserted through an endoscope for minimally invasive procedures. Laser-tissue interaction is the other significant difference. The CO2 laser is completely absorbed by water, which limits the effect to visible tissue. The diode wavelength is minimally absorbed by water and may affect tissue as deep as 10 mm below the surface in the free-beam mode. With proper respect for the tissue effect, these differences can be used to the advantage of the patient.

Animals↗
PubMed1991

Stented laser-welded vasovasostomy in the rat: comparison of Nd:YAG and CO2 lasers.

In 54 male Sprague-Dawley rats, 108 vasovasostomies were performed. Sutureless laser welding with the assistance of a removable stent was done using a CO2- and an Nd:YAG-laser system. Conventional two-layer microsurgical anastomoses served as controls. The Nd:YAG laser resulted in significantly lower patency rates, with a higher percentage of sperm granulomas; the CO2 laser produced results equivalent to conventional suturing. Sutureless laser welding utilizing a removable stent proved to be a time- and cost-saving procedure for vasovasostomies in the rat.

Animals↗
PubMed2003

Semianalytical thermal model for subablative laser heating of homogeneous nonperfused biological tissue: application to laser thermokeratoplasty.

We present a semianalytical technique to calculate the temperature in homogeneous nonperfused tissue during subablative laser heating. Analytical expressions of the temperature distribution in time and space are provided for collimated beams with Gaussian and top-hat intensity distributions perpendicularly incident on a finite tissue slab. The temperature distribution produced with a collimated Gaussian beam is the triple sum of the product of four functions of separate variables. The semianalytical technique can be used to rapidly calculate the temperature in laser-irradiated tissue at any point in time and space. The model was used to estimate the corneal temperature during pulsed holmium:YAG laser thermokeratoplasty with various boundary conditions at the anterior and posterior corneal surface. The model demonstrates that the corneal temperature during laser thermokeratoplasty (LTK) with a pulsed Ho:YAG laser may be sufficient to induce superficial vaporization of epithelial cells and local thermal damage to the endothelium. The calculations show that convection at the anterior corneal surface does not have a significant effect on the corneal temperature distribution, but that a better knowledge of the cooling effect of the aqueous is required to better estimate the corneal temperature distribution during LTK.

Computer Simulation↗
PubMed2006

Does the source of laser energy influence the coagulation of chorionic plate vessels? Comparison of Nd:YAG and diode laser on an ex vivo placental model.

OBJECTIVES: To compare the histological effects of diode and Neodymium-Yttrium Aluminium Garnet (Nd:YAG) laser coagulation of chorionic plate vessels. METHODS: In selected chorionic plate vessels in an ex vivo term placenta perfused with warm saline solution, diode (wavelength 940 nm) and Nd:YAG (wave length 1,064 nm) laser were used with an output of 30, 40, and 50 W, and 55 and 70 W respectively using preset energy and duration of impact. All vessels were examined histologically blindly to the procedures' characteristics. RESULTS: A total of 23 vessels were coagulated. Similar histological lesions were observed using diode and Nd:YAG lasers. The lesions were compatible with an acceptable clinical effect at all power outputs tested. The results were not related to the diameter or type of vessels. Lesions of the endothelium and reduction of the vessel lumen were best achieved with a diode laser at 40 W. CONCLUSION: Nd:YAG and Diode laser induce significant and comparable changes in chorionic plate vessels compatible with an efficient coagulation process under the experimental condition used.

Aluminum↗
PubMedDate not supplied

Laser in situ keratomileusis vs. laser epithelial keratomileusis (LASIK vs. LASEK).

PURPOSE: To compare results of laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) for the treatment of myopia. METHODS: Two groups of fifteen patients (30 eyes) each were assigned to either the LASIK group or the LASEK group. LASIK procedure: A Hansatome microkeratome with the ring at 9.5 mm was used to create the corneal flap (depth, 160 microm). The myopic correction was then registered on the Nidek EC-5000 excimer laser and the appropriate ablation performed. LASEK procedure: Twenty percent ethyl alcohol was placed within the corneal epithelial ring. An intact epithelial flap was retracted. The Nidek EC-5000 excimer laser was applied in a similar manner to the LASIK procedure. Patients from both groups were followed postoperatively for 6 months, measuring best spectacle-corrected visual acuity, contrast sensitivity, and corneal topographic meridians of 3 mm, 5 mm, and 7 mm. RESULTS: Comparing corneal topography, best spectacle-corrected visual acuity, and contrast sensitivity data, refractive results in the LASEK group were better than the LASIK group. CONCLUSION: Objective data show that with the Nidek EC-5000 excimer laser, the LASEK method of corneal splitting may prove superior to the LASIK method.

Adult↗
PubMed2002

[Lasers in dentistry 1. What is special about lasers?].

Diagnosis and treatment with lasers is becoming widely spread in dentistry. This article is an introduction to a series of articles that deal with the many dental applications of lasers. The article contains a summary of presently used lasers. It also describes the pertinent features of laser radiation: parallelism of the beam and narrow line shape in the spectrum of electromagnetic radiation. Finally, it summarizes the relevant processes of interaction of laser radiation with tissue: scattering, absorption, fluorescence and frequency-doubling.

Dental Instruments↗
PubMed2002

[Lasers in dentistry 8. Use of lasers in oral and maxillofacial surgery].

Since the 1970's lasers are used in oral and maxillofacial surgery. The effect of a laser on tissue is determined by the wavelength of the laserlight and the tissue specific absorbtion. Lasers are used for evaporation, excision and coagulation of tissue. The CO2-laser, the Nd:YAG-laser and the Argonlaser are used for these purposes. Light and laserlight are used for the diagnosis of mucosal lesions. By using different excitation wavelength autofluorescence of lesions can be detected and analysed. An artificial neural network can be used to analyse these data. Photodynamic Therapy (PDT) is a cancer therapy based on the more or less specific absorption of a drug in tumour, that can be activated with light of a specific wavelength. Activation of this drug causes tumour destruction due to the formation of oxyginradicals. PDT is limited by the penetration of the activating light and is therefore only suitable for the treatment of superficial tumours.

Humans↗
PubMed1990

[Laser lithotripsy with the neodymium YAG laser].

Laser-induced shock wave lithotripsy (LISL) with a Q-switched neodymium-YAG laser depends on the generation of a laser-induced breakdown in the fluid surrounding the stone. An oscillating plasma bubble is created, directing shock waves towards the stone. These cavitational effects fragment the calculus into small particles. A new bifunctional laser is introduced: this allows both nanosecond pulses for shock wave generation and disintegration of urinary calculi and millisecond pulses for biliary stones and tissue coagulation. It can be supplied with 320-, 400-, and 600-micron fibers. We have treated 189 ureteric stones in 185 patients with laser lithotripsy utilizing flexible ureteroscopes (n = 26) or rigid ureteroscopes (n = 159). It proved possible to fragment 179 stones into small pieces. In eight patients LISL was not successful. A rigid cystoscope that can be dismantled into an upper and lower hemisheath for the introduction of flexible endoscopes into the ureter without prior dilatation of the ureteral orifice was used in 15 patients.

Cystoscopes↗
PubMed1993

Stapedectomy surgery in residency: KTP-532 laser versus argon laser.

Stapedectomy for otosclerosis is one of the most demanding otologic procedures, especially for residents in training. The reported series in the literature, as well as our own experience with the traditional resident-performed complete stapedectomy, have been disappointing. The number of patients available to train residents in stapedectomy techniques has steadily declined. The challenge to the otologist involved in teaching residents and fellows is to find a method that will be safe and effective. Over the past 5 years, we have had an opportunity at the University of Texas Medical Branch at Galveston to compare two methods of performing a laser stapedotomy. The two methods involve using the KTP-532 laser with a micromanipulator and using the hand-held argon laser. Although the wavelengths of these two lasers are similar, the methods used in applying them are very different. Twenty-five consecutive cases in each group were reviewed with regards to technical difficulty, complication rate, operative time, and air-borne gap closure. The hand-held argon laser emerged as the preferred technique for teaching a routine stapedotomy to residents.

Adult↗
PubMed1996

[Possibilities for the us of laser surgery in veterinary medicine. Part 2: Effects of laser beams on tissue].

The effect of a certain laser beam on tissue is dependent on the different properties of the tissue. The various kinds of laser radiation are absorbed from different components of an organ. Only where absorption takes place there will be a transformation of the energy of radiation to other forms of energy and changes in tissue will occur. The arising thermal energy not only heats the area exposed to the laser beam but the surrounding tissue. The extent of the heating effect on tissue is due to properties of the tissue, e.g. the degree of blood supply and with it the draining of heat, and the parameters of the laser system, e.g. time of exposition and power of radiation. By increasing power of radiation the effect will be an unspecific heat stimulation, coagulation of tissue up to vaporization of tissue. By using different ways of transmission the effects produced by laser will change and can be adapted to various medical and anatomical requirements.

Animals↗
PubMed1999

Treatment of benign and atypical nevi with the normal-mode ruby laser and the Q-switched ruby laser: clinical improvement but failure to completely eliminate nevomelanocytes.

OBJECTIVE: To evaluate the effect of normal-mode and Q-switched ruby laser light (694 nm) on nevomelanocytes of benign, atypical, and congenital nevi. DESIGN: Half of the lesion of each of 31 nevi was treated with either the Q-switched ruby laser or the normal-mode ruby laser or both; the other half of the lesion was covered with aluminum foil and was not treated. SETTING: A university-affiliated, hospital-based laser center. PATIENTS: Sixteen patients with a total of 31 melanocytic nevi were enrolled in the study. INTERVENTIONS: All nevi were evaluated by at least 2 dermatologists to assess the degree of clinical atypia. Photographs were taken before and immediately after treatment and at each follow-up visit. The digital imaging system was used to evaluate the number of melanocytes in a measured length of basement membrane zone. MAIN OUTCOME MEASURE: Three individual readings (number of melanocytes per unit length) were taken on both the control and treated halves and then compared to quantitate treatment effect. All analyses used averages from 3 measurements. A Student paired t test was used to compare the treated and untreated sides. RESULTS: Sixteen (52%) of the nevi showed a clinically visible decrease in pigment on the treatment side at the 4-week follow-up visit. CONCLUSION: No lesions had complete histologic removal of all nevomelanocytes. Therefore, 1 or 2 laser treatments are not sufficient to cause complete removal of a lesion either clinically or histologically.

Adolescent↗
PubMed1990

Laser sclerostomy by pulsed-dye laser and goniolens.

We describe an ab-interno laser sclerostomy procedure using the method termed dye-enhanced ablation with a slit-lamp delivery system and special goniolens such that only the laser light beam penetrates the anterior chamber. The procedure uses a microsecond-pulsed-dye laser emitting at 666 nm and iontophoresis of methylene blue dye (absorption of 668 nm) into the sclera at the limbus to enhance the absorption of the laser light. We compared the number of pulses needed to perforate excised human sclera at pulse durations of 1.5, 20, and 300 microseconds. Pulse durations of 1.5 and 20 microseconds required 20 pulses or fewer to perforate excised human sclera with pulse energies of 75 to 100 mJ. The ab-interno laser sclerostomy procedure was performed in 54 eyes of Dutch-belted rabbits with pulse durations of 1.5 or 20 microseconds and a 100- or 200-microns incident spot diameter delivered using a CGF goniolens. Full-thickness fistulas were successfully created at both pulse durations in approximately 80% of eyes treated. A range of three to 25 pulses was required to perforate sclera with slightly fewer pulses and lower pulse energies at 1.5 microseconds compared with 20 microseconds. There were no significant complications from the procedure. This technique could permit filtration surgery to be performed on an outpatient basis.

Animals↗
PubMed1993

Comparison of excimer laser treatment of astigmatism and myopia. The Excimer Laser and Research Group.

OBJECTIVE: To assess the safety and efficacy of excimer laser treatment of myopic astigmatism and to compare this with the excimer laser treatment of myopia. DESIGN: A prospective, open study of consecutive patients having excimer laser treatment of myopic astigmatism or myopia. SETTINGS: Patients were recruited from 18 private ophthalmic practices. PATIENTS: Fifty-four eyes received treatment for astigmatism and 66 eyes for myopia. One patient was lost to follow-up, and another underwent an ineffective ablation. INTERVENTIONS: A VISX Twenty/Twenty excimer laser was used to perform either photoastigmatic refractive keratectomy or photorefractive keratectomy. MAIN OUTCOME MEASURES: Refraction and visual acuity with and without correction were assessed preoperatively and postoperatively. RESULTS: At 6 months, 17 (85%) of the 20 patients receiving photoastigmatic refractive keratectomy were within 1 diopter of plano refraction, and 19 (95%) of 20 had uncorrected visual acuity of 6/12 (20/40) or better. For patients receiving photorefractive keratectomy, these figures were 28 (88%) of 32 patients and 28 (88%) of 32 patients, respectively. CONCLUSIONS: Excimer laser surgery offers an effective option in the treatment of myopic astigmatism.

Adult↗
PubMed1996

Two-lasers assisted ablation: a method for enhancing conventional laser ablation of materials.

A new method for enhanced ablation by pulsed laser radiation has been demonstrated. The method utilizes an "impulse" ablation laser in conjunction with cyclical heating of the tissue by an auxiliary source: the "primer." In this study we use an auxiliary laser as the "primer" heat source, which sets up a thermal and stress field modulation in the target material. The cyclical stress associated with the thermal modulation reduces material strength thus enhancing ablation (larger mass removed per pulse) by the "impulse" laser. Ablation rate enhancement of more than twice the single-laser value is demonstrated.

Hot Temperature↗