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At least 163 records · Page 9Linked to original sources

PubMed2006

Melanin granule models for the processes of laser-induced thermal damage in pigmented retinal tissues. I. Modeling of laser-induced heating of melanosomes and selective thermal processes in retinal tissues.

The computer modeling was applied for investigation of the processes of laser-induced tissue damage. The melanin granule models for the processes of laser-induced thermal damage and the results of computer modeling of the optical, thermophysical, and thermochemical processes during selective laser interaction with melanoprotein granules (melanosomes) in retinal pigment epithelium are presented in this paper. Physical-mathematical model and system of equations are formulated which describe thermal interaction processes for "short" laser pulses of duration t (p)<10(-6) s and for " long' pulses of duration t(p) > 10(-6) s. Results of numerical simulation of the processes give the space-time distributions of temperature and degrees of thermodenaturation of the protein molecules inside and around melanosomes and in the volume of irradiated tissues. Energy absorption, heat transfer and thermochemical (thermodenaturation, coagulation) processes occurring during the interaction of laser pulses with pigmented spherical and spheroidal granules in heterogeneous tissues are theoretically investigated. The possibility for selective interaction of short laser pulses with pigmented granules is discussed which results in the formation of denaturation microregions inside and near the pigmented granules (granular thermodenaturation) without origination of a continuous macroscopic thermodenaturation lesion in tissue. Analytical model of heating of single spherical and spheroidal granule under laser pulse is presented. Simple equations for time dependencies of particle temperature are obtained. The presented results are of essential interest for laser applications in and can be used for investigation of laser interaction with pigmented tissues in different fields of laser medicine.

Computer Simulation↗

PubMedDate not supplied

The resistance to carbon dioxide laser ignition of a new endotracheal tube: Xomed Laser-Shield II.

STUDY OBJECTIVE: To assess the resistance of a new endotracheal tube to penetration and ignition by a carbon dioxide (CO2) laser at a clinically relevant power setting. DESIGN: An unblinded, in vitro trial simulating clinical conditions. SETTING: The operating room at a university medical center. PATIENTS: None. INTERVENTIONS: A CO2 laser at 20W with a beam diameter of 1 mm was directed onto the Xomed Laser-Shield II at several points: both perpendicular and tangential to the portion of the tube covered by the protective wrap, to the unwrapped silicone tubing just proximal to the cuff, to the cuff filled with saline and methylene blue, and to the unwrapped silicone tubing distal to the cuff. Trials were performed with or without supplemental oxygen (O2) blown onto the study site and with a 6 L/min flow through the tube containing one of four concentrations of O2 in O2-air admixtures: 21%, 30%, 40%, and 100%. MEASUREMENTS AND MAIN RESULTS: Under all conditions, the laser did not penetrate the protective wrap, but the overlying polytetrafluoroethylene (Teflon) sheet was vaporized to an area equal to the size of beam application. The cuff was penetrated by the laser within 5 seconds. The unprotected silicone protein of the tube was penetrated by the laser in approximately 5 seconds, and time to formation of a blowtorch phenomenon shortened with increasing the percentage of O2 flowing through the tube. CONCLUSIONS: The protective coating of the Xomed Laser-Shield II is laser-resistant, but the unprotected silicone proximal and distal to the cuff is laser-vulnerable and can, under certain conditions, promote a blowtorch phenomenon. This tube would be acceptable for use in oral and pharyngeal laser surgery, but we recommend its use only in well-ventilated areas, out of concern for exposure to the products of the pyrolysis of Teflon, specifically the development of polymer-fume fever.

Equipment Design↗

PubMedDate not supplied

Prevention of CO2 laser-induced endotracheal tube fires with the laser-guard protective coating.

STUDY OBJECTIVE: To determine how well Laser-Guard protects polyvinyl chloride (PVC) endotracheal tubes from the carbon dioxide (CO2) laser. DESIGN: Bare and Laser-Guard-protected PVC endotracheal tubes were tested with 5 L/min of oxygen (O2) passing through them. SETTING: Research laboratory of a university-affiliated metropolitan medical center. INTERVENTIONS: After moistening the Laser-Guard-protected endotracheal tubes, we subjected the tubes to CO2 laser radiation at 10 and 70 watts until combustion occurred or 60 seconds had elapsed. MEASUREMENTS AND MAIN RESULTS: The bare PVC tube ignited and a "blowtorch" fire occurred after 3 seconds of CO2 laser use at 70 watts. The moistened Laser-Guard-protected PVC endotracheal tubes were not significantly damaged by 1 minute of laser use at 70 watts. CONCLUSIONS: Laser-Guard protects the shafts of combustible PVC endotracheal tubes from direct, high-power, continuous CO2 laser radiation.

Accidents, Occupational↗

PubMed1999

Combination treatment of melasma with pulsed CO2 laser followed by Q-switched alexandrite laser: a pilot study.

BACKGROUND: Melasma is very difficult to treat and often refractory to treatment with topical creams and pigmented-lesion lasers. OBJECTIVE: Pulsed CO2 laser alone is compared with the combination of pulsed CO2 laser followed by Q-switched alexandrite laser in the treatment of dermal-type melasma. This combination is proposed to be effective by first destroying the abnormal melanocytes with the pulsed CO2 laser and then selectively eliminating the dermal melanin with the alexandrite laser. METHODS: Four patients were randomly chosen for each treatment arm. There were multiple follow-up visits for examination by an objective blinded investigator. RESULTS: All patients in the combination laser group showed complete resolution, and two patients in the CO2 laser only group had peripheral hyperpigmentation in the long-term follow-up evaluation. CONCLUSION: These laser therapies are safe, as there was no scarring and no infection. The combination laser therapy was highly effective in removing the hyperpigmentation and all patients in this group showed complete resolution without any peripheral hyperpigmentation.

Beryllium↗

PubMed1995

[Treatment of vascular malformations and pigment disorders of the face and neck by pulsed dye laser, Photoderm VL and Q-switched ruby laser].

BACKGROUND: Two new types of lasers, the pulsed dye laser and the Q-switched ruby laser, have shown good to excellent results in the treatment of vascular malformations and benign pigmented lesions of the skin. A new and very effective alternative to pulsed dye laser is the recently introduced Photoderm VL. This device is based on the use of a wide-band non-coherent intense pulsed light source which emits a continuous spectrum in the range of 515 nm to 1200 nm. PATIENTS AND METHODS: More than a 1000 patients with a variety of lesions of the skin were treated by these new laser systems and the Photoderm VL. The Q-switched ruby laser (wavelength 694 nm, pulse duration 25 ns) is suitable for the treatment of benign lentigines, café-au-lait macules, seborrhoic ceratosis, tattoos, and traumatic tattoos. The pulsed dye laser (585 nm, 0,3-0,45 ms) treats nevi flammei, capillary hemangiomas, telangiectasias, xanthelasma, hypertrophic scarring, and adenoma sebaceum. In addition we present the facilities of the new Photoderm VL (515 nm-1200 nm, 0,5-20 ms) for the treatment of nevi flammei, benign hemangiomatous malformations, telangiectasias, erythrosis interfollicularis colli, hypertrophic scarring, and hypertrichosis. RESULTS AND CONCLUSIONS: the Q-switched ruby laser, the pulsed dye laser, and the Photoderm VL show excellent results in the treatment of lesions of the skin, which otherwise would have been difficult to treat of untreatable. The efficiency of the laser types presented is based on the theory of selective photothermolysis. Scarring is almost never seen and hypo- or hyperpigmentation is in most cases transient.

Adolescent↗

PubMed1990

[Color vision disturbance in laser operators and patients: comparison of argon and dye lasers].

Color contrast sensitivity was measured in laser operators before and after laser sessions. The tritan threshold was elevated after the sessions in all laser operators who had used argon (blue-green) lasers. No change was observed when lasers with longer wave-lengths were used. Elevation of the tritan threshold to above-normal levels was observed even before laser sessions. The thresholds remained increased even when the laser operator did not use a laser for 3 weeks. Thus, it appears that the damage caused by the argon blue-green laser is cumulative. Elevated tritan thresholds were also observed in patients with peripheral retinal breaks who were treated with an argon (blue-green) laser.

Adolescent↗

PubMed2000

Successful removal by ruby laser of darkened ink after ruby laser treatment of mismatched tattoos for acne scars.

Cosmetic tattoos are becoming increasingly popular. Elimination of cosmetic tattoos is sought because of misplacement or migration of tattoo pigment, allergic reactions to the various pigments or dissatisfaction of the customer for various reasons. Removal of unwanted pigment is a domain of laser surgery using various Q-switched laser systems, such as the ruby, alexandrite, pulsed dye and Nd:YAG lasers. Dark colours are easily removed by these lasers, whereas red, pink and skin-toned pigment may turn black if exposed to Q-switched laser light. This ink-blackening occurs because Q-switched lasers heat up the pigments, which consist of ferric oxide, and reduce them into ferrous oxide, which is black. Laser-induced black ink is not always readily removed. A successful ruby laser-removal of laser-induced blackened cosmetic tattoos for acne scar camouflage is reported. The advantageous outcome in this case contrasts with other published cases where laser-darkened pigment had to be removed by other measures, or was permanent. Test site treatment can limit the problem to some degree but, in addition to test-treating, some kind of 'tattoo identification card' could help to prevent problems in this field and allow 'in vitro' test treatment.

Acne Vulgaris↗

PubMed1983

Optical radiation hazards of laser welding processes. Part 1: Neodymium-YAG laser.

High power laser devices are being used for numerous metalworking processes such as welding, cutting and heat treating. Such laser devices are totally enclosed either by the manufacturer or the end-user. When this is done, the total laser system is usually certified by the manufacturer following the federal requirements of the Code of Federal Regulations (CFR) 1040.10 and 10.40.11 as a Class I laser system. Similarly, the end-user may also reclassify an enclosed high-power laser into the Class I category following the requirements of the American National Standards Institute (ANSI) Z-136.1 (1980) standard. There are, however, numerous industrial laser applications where Class IV systems are required to be used in an unenclosed manner. In such applications, there is concern for both ocular and skin hazards caused by direct and scattered laser radiation, as well as potential hazards caused by the optical radiation created by the laser beam's interaction with the metal (i.e. the plume radiation). Radiant energy measurements are reported for both the scattered laser radiation and the resultant plume radiations which were produced during typical unenclosed Class IV Neodymium-YAG laser welding processes. Evaluation of the plume radiation was done with both radiometric and spectroradiometric measurement equipment. The data obtained were compared to applicable safety standards.

Accidents, Occupational↗

PubMed1998

Scanning laser ophthalmoscope microperimetric assessment in patients with successful laser treatment for juxtafoveal choroidal neovascularization.

PURPOSE: To evaluate fixation stability and changes in retinal function in patients with laser scar expansion after successful macular photocoagulation for juxtafoveal choroidal neovascularization (CNV). METHODS: A consecutive series of 35 patients was examined in this prospective study. Only patients who had been successfully treated with laser photocoagulation for juxtafoveal CNV and who could be followed over a period of at least 6 months were enrolled. Fixation stability and localized light sensitivity were examined by microperimetry using a scanning laser ophthalmoscope. Visual acuity was measured 2 weeks and 3 and 6 months after the laser treatment. The correlation between changes in the logarithm of the minimum angle of resolution (LogMAR) visual acuity and the distance between fixation and the center of the fovea was evaluated. RESULTS: Of 22 eyes of 20 patients that underwent data analysis, laser scar expansion was observed in 16 (72.7%). Ten (62.5%) of the 16 eyes had relative scotomas corresponding to the expanded laser scars. Mean laser scar expansion ratio was 28.7% in the ARMD group and 109.2% in the myopia group, a statistically significant difference (P < 0.01). The change in LogMAR visual acuity was significantly correlated with the distance of fixation locus from the center of the fovea (r = 0.76). CONCLUSIONS: Laser scars produced by photocoagulation for juxtafoveal CNV may expand and extend into the fovea, causing secondary retinal dysfunction. Scanning laser ophthalmoscopic assessment may be useful in evaluating fixation stability and subclinical changes in retinal function surrounding the laser scars before visual disturbance appears.

Aged↗

PubMed2004

Comparison of a 1450-nm diode laser and a 1320-nm Nd:YAG laser in the treatment of atrophic facial scars: a prospective clinical and histologic study.

BACKGROUND: Atrophic scar revision techniques, although numerous, have been hampered by inadequate clinical responses and prolonged postoperative recovery periods. Nonablative laser treatment has been shown to effect significant dermal collagen remodeling with minimal posttreatment sequelae. Although many studies have been published regarding the effectiveness of these nonablative lasers on rhytides, there are limited data demonstrating their specific effects on atrophic scars. OBJECTIVE: To evaluate and compare the efficacy and safety of long-pulsed 1320-nm Nd:YAG and 1450-nm diode lasers in the treatment of atrophic facial scarring. METHODS: A series of 20 patients (skin phototypes I-V) with mild to moderate atrophic facial acne scars randomly received three successive monthly treatments with a long-pulsed 1320-nm Nd:YAG laser on one facial half and a long-pulsed 1450-nm diode laser on the contralateral facial half. Patients were evaluated using digital photography and three-dimensional in vivo microtopography measurements at each treatment visit and at 1, 3, 6, and 12 months postoperatively. Histologic evaluations of cutaneous biopsies obtained before treatment, immediately after the first treatment, and at 1, 3, 6, and 12 months after the third treatment were performed. Clinical assessment scores were determined at each treatment session and follow-up visit. Patient satisfaction surveys were obtained at the end of the study. RESULTS: Mild to moderate clinical improvement was observed after the series of three treatments in the majority of patients studied. Patient satisfaction scores and in vivo microtopography measurements paralleled the photographic and histopathologic changes seen. Side effects of treatment were limited to mild transient erythema, edema, and hyperpigmentation. No scarring or adverse textural changes resulted from the use of either laser system. CONCLUSIONS: Nonablative long-pulsed 1320-nm Nd:YAG and 1450-nm diode lasers each offer clinical improvement for patients with atrophic scarring without significant side effects or complications. The 1450-nm diode laser showed greater clinical scar response at the parameters studied. The use of nonablative laser systems is a good treatment alternative for patients with atrophic scarring who are unable or unwilling to endure the prolonged postoperative recovery process associated with ablative laser skin resurfacing procedures.

Acne Vulgaris↗

PubMed1993

Comparison of retinal lesions produced by transscleral krypton laser photocoagulation, transpupillar krypton laser photocoagulation and cryocoagulation.

We compared the retinal lesions produced by transscleral and transpupillar krypton lasers and cryocoagulation. Transscleral laser photocoagulation was applied under indirect ophthalmoscope visual control with indentation of the sclera by the laser probe. Transpupillar laser was performed with a Volk 90D lens. The power and the spot size were adjusted to create lesions of similar size and intensity as in transscleral photocoagulation. The output power needed for transscleral photocoagulation was 0.2W with exposure time of 3-5 sec. In the transpupillar photocoagulation the output power was 0.3W and the exposure time 2-3 sec, respectively. The lesions were studied histologically 1h, 1, 3, 7, 30 and 60 days after treatment. Histopathological studies of the krypton laser lesions revealed destruction and scarring of the outer layers of the retina and the choroid. The lesions produced by transpupillar and transscleral laser appeared to be rather similar. These results indicate that, in the rabbit eye, there is no difference between the lesions produced by the transpupillar or transscleral route of laser application. Transscleral laser application may have clinical advantages over transpupillary laser in the eyes with hazy media or in other cases when transpupillar laser is not possible.

Animals↗

PubMed2005

Laser-induced breakdown spectroscopy analysis of solids using a long-pulse (150 ns) Q-switched Nd:YAG laser.

Laser-induced breakdown spectroscopy (LIBS) measurements are typically carried out using pulses (<20 ns, >50 mJ) from a flashlamp-pumped electro-optically Q-switched Nd:YAG laser (EO-laser) or excimer laser. Here we report LIBS analyses of solids using an acousto-optically Q-switched Nd:YAG laser (AO-laser) producing 150 ns pulses of lower energy (10 mJ) at repetition rates up to 6 kHz. The high repetition rate allows increased spatial or depth sampling over a given time period compared to the EO-laser. Results of AO-laser based LIBS analysis of (1) steels, (2) soils, and (3) surface stains and dusts are described. Detection limits for Cr, Cu, Mn, Ni, and Si in steel ranged from 0.11 to 0.24% using a commercial polychromator-based detection system with limits 4--30 times lower achieved using a laboratory-based detection system. The minimum detectable masses of Ba, Cr, Mn, and Sr on a metal surface were estimated with 1.2 pg/shot achieved for Sr. Detection limits for Ba and Sr in soil were 296 and 52 ppm, respectively. The temperatures, spectra, and emission decay curves from plasmas generated by the AO- and EO-lasers are compared and some characteristics of particles ablated by the AO-laser are described.

Environmental Monitoring↗

PubMed1993

Loss of vasoreactivity by laser thermal energy or argon laser irradiation.

Vasoreactivity of laser-treated vessels was investigated in two different experimental conditions. The canine left circumflex coronary artery (LCx) was lased under perfusion with Krebs-bicarbonate buffer by means of a thermal laser (hot-tip probe, HT) at 7 W for 6 seconds and an argon laser beam through a 300 microns optical fiber at 3 W (tip power) for 1 second at 12 spots. A nontreated segment of the LCx served as a control. Two 3-mm long segments were obtained from the treated segment: one to measure the results of potassium (K) induced contraction, and another 3, 4 diaminopyridine (DAP; K channel inhibitor) induced contraction. In 11 instances, coronary angiography of the perfused artery showed less than 50% stenosis after laser treatment. The segments were then mounted isometrically with 1 g tension in Krebs-bicarbonate buffer. Contraction was induced either with 30 mM KCI or 10(-2) M DAP and expressed as developed tension (gram; g). KCI induced vasocontraction of 4.15 +/- 0.93 g in the control, 0.33 +/- 0.71 g in laser irradiated segments (P < 0.0001 vs control), and 0.02 +/- 0.06 g in thermally-treated segments (P < 0.0001 vs control). DAP induced vasocontraction of 5.21 +/- 1.32 g in the control, 0.39 +/- 0.83 g in laser irradiated segments (P < 0.0001 vs control), and 0.07 +/- 0.13 g in thermally treated segments (P < 0.001 vs control). In 4 instances, more than 50% stenosis remained and additional balloon dilatation reduced the stenosis to less than 50%. The lesions also showed reduced vasoreactivity. In vivo thermal angioplasty resulted in reduced vasoreactivity compared to control in 4 anesthetized dogs. Thus, laser and thermal angioplasty reduced vasoreactivity induced by either KCI or 3, 4 DAP. Neither acetylcholine at 10(-6) M nor papaverine at 10(-4) M was able to induce relaxation of treated segments. In conclusion, 1) the lased coronary artery loses its vasoreactivity to either a constrictive or relaxing agent, 2) although stenosis may be produced by laser energy, additional balloon dilatation can reduce residual stenosis, and 3) laser thermal or argon laser angioplasty may prevent severe coronary spasm.

4-Aminopyridine↗

PubMed2005

Endovenous treatment of the great saphenous vein using a 1,320 nm Nd:YAG laser causes fewer side effects than using a 940 nm diode laser.

BACKGROUND: Limited data are available about treatment-related side effects with respect to laser wavelength in endovenous laser treatment (ELT) of the great saphenous vein (GSV). OBJECTIVE: To compare the results and side effects of a 940 nm diode and a 1,320 nm neodymium:yttium-aluminum-garnet (Nd:YAG) laser. METHODS: Three patient cohorts (A, B, and C) received ELT of the GSV using a 940 nm diode laser at 15 W (group A) or 30 W (group B) or using a 1,320 nm laser at 8 W (group C). In all cases, energy was administered continuously with constant pullback of the laser fiber under perivenous tumescent local anesthesia. RESULTS: The GSVs of group A (n = 113), group B (n = 136), and group C (n = 33) received ELT. An average linear endovenous energy density of 24, 63, and 62 J/cm and an average endovenous fluence equivalent of 12, 30, and 33 J/cm2 were administered to the vein. Occlusion rates were 95% (group A), 100% (group B), and 100% (group C) at day 1 after ELT and 90.3% (group A), 100% (group B), and 97% (group C) at 3 months after ELT. With the 1,320 nm laser ELT (group C), treatment-related pain (50%) and the need for analgesics (36%) were significantly reduced (p < .005) in comparison with treatment-related pain (81%) and the need for analgesics (67%) after the 30 W 940 nm laser ELT (group B). Ecchymosis was also significantly reduced (p < .05) in group C (1,320 nm) compared with group B (30 W, 940 nm). CONCLUSION: ELT of the GSV using a 1,320 nm Nd:YAG laser causes fewer side effects compared with 940 nm diode laser ELT.

Adolescent↗

PubMedDate not supplied

In vivo comparison of a twin wavelength laser Doppler flowmeter using He-Ne and laser diode sources.

This paper reports the results of a preliminary in vivo investigation in which laser Doppler blood-flow measurements were made in a variety of tissues in the anaesthetized rat using a twin wavelength laser Doppler system. The aim was to assess whether there was any detectable difference in the depth response of the laser Doppler system to blood-flow in skin, muscle and brain tissue using red light (633 nm) from a He-Ne laser source and near infrared (NIR) light (780 nm) from a semiconductor diode laser source. The results show that under normalized conditions, the flow signals obtained from the near infrared laser Doppler system is consistently larger than that recorded from the red He-Ne laser Doppler system. This suggests that laser Doppler flowmetry systems based on NIR laser sources sample larger volumes of tissue than those based on red He-Ne lasers.

Animals↗

PubMedDate not supplied

The picosecond laser for nonmechanical laser in situ keratomileusis.

PURPOSE: To introduce the clinical use of the Nd:YLF picosecond laser as a nonmechanical microkeratome. METHODS: A commercially available Nd:YLF picosecond laser (25 microJ/pulse, 30 psec, 1053 nm) was used to deliver intrastromal pulses of focused high power laser light to generate a flap for laser in situ keratomileusis (LASIK) and perform picosecond laser keratomileusis (PLK) in two partially sighted patients with high myopia. RESULTS: Case #1: A 6 mm, 150 microns flap for LASIK was successfully created and the underlying stroma treated with an excimer laser for a target correction of -15.00 D of myopia. Good corneal clarity and a refractive change of -14.00 D was recorded 2 months postoperatively. Case #2: Both eyes of a high myope (-22.00 D right eye, -21.50 D left eye) underwent picosecond laser keratomileusis, removing a 3.2 mm diameter lenticule of 120 microns thickness under a 200 microns flap. Postoperative refraction was -2.00 D at 7 months in the right eye and -0.75 D at 2 months in the left eye with improvement of spectacle-corrected visual acuity from 20/200 to 20/70 in each eye. CONCLUSION: The Nd:YLF picosecond laser can be safely used in creating a corneal flap for LASIK and in performing picosecond laser keratomileusis for high myopia. Future refinements in the laser will include a larger flap diameter and femtosecond pulsing capability.

Corneal Stroma↗

PubMed1996

[A basic study of the interstitial laser prostatectomy using pulsed holmium: yttrium-aluminum-garnet (Ho:YAG) laser].

BACKGROUND: To develop a new procedure for laser prostatectomy through a biopsy needle, we evaluated the efficacy of interstitial laser irradiation with a pulsed Ho:YAG laser (lambda: 2.1 microns) in the normal canine prostate. METHODS: Pathological studies were performed up to 6 months after interstitial laser irradiation in 26 mongrel dogs (15.4 +/- 2.6 kg). Two dogs underwent the identical procedures without irradiation as controls (control group). Prostate glands of the other 24 dogs were irradiated interstitially with a Ho:YAG laser through a silica glass fiber (400 microns phi). In one prostate, each lobe was irradiated with 500 J/cm2 or 150 J/cm2 in energy density (fluence). Four prostates were irradiated with 150-175 J/cm2 in fluence (low-fluence group). Nineteen prostates were irradiated with 500-600 J/cm2 in fluence (high-fluence group). Prostates glands were excised immediately, 1 month, 2 months, 3 months, or 6 months after irradiation and examined histologically. To investigate the influence of interstitial irradiation with a Ho:YAG laser on smooth muscle and/or on the adrenergic activity of the prostate, we also measured changes in intraluminal pressure of the prostatic urethra upon administration of epinephrine (10 micrograms/kg) in six dogs before and after irradiation. We developed a novel three-membrane balloon catheter with an open end for measuring this pressure change. RESULTS: Specimens harvested immediately in control and low-fluence groups showed slight hemorrhage in areas surrounding the punctured or irradiated site, but the surrounding smooth muscles or small vessels were not destroyed. In the high-fluence group, smooth muscles and small vessels approximately 1 mm thick that surrounded the ablated hole were destroyed, but the thickness of the thermal coagulation layer was only approximately 0.2 mm. These findings suggested that damage to the small vessels and smooth muscle may have been caused by laser-induced stress waves rather than by a thermal effect. In the control and low-fluence groups, prostatic volume remained unchanged 1 month after puncture or low-fluence irradiation. In the high-fluence group, huge cavities were created in the laser-irradiated prostate gland 1 or 2 months after irradiation and prostatic volume was reduced maximally by 60%. In the high-fluence group, the cavities collapsed and prostatic volume was reduced by up to 50% at 6 months post-procedure. The prostatic urethra expanded following the reduction in volume. The maximal intraluminal change in pressure of the prostatic urethra decreased significantly after laser irradiation (p < 0.05). CONCLUSION: Results indicate that interstitial irradiation of the prostate with a Ho:YAG laser with high-fluence may relieve the anatomical and functional obstruction of the prostatic urethra in benign prostatic hyperplasia.

Animals↗

PubMed1995

Laser hair transplantation. Tissue effects of laser parameters.

BACKGROUND: Micro- and minigrafting have become increasingly popular in hair transplantation over the past decade, resulting in larger numbers of grafts per session and lengthy, potentially technically difficult procedures. The advent of very high energy pulsed carbon dioxide lasers as surgical instruments has led to the investigation of their use in hair transplantation, as bloodless surgery with tissue removal by vaporization has obvious advantages as far as surgical speed is concerned. METHODS: A prospective study of eight patients comparing conventional micro- and minigrafting using 18- and 14-gauge needle punctures with dilators versus laser-vaporized donor sites with variation of laser parameters was conducted with monthly evaluation of healing and hair growth for 6 months. In addition, an in vitro histological study of laser vaporization recipient sites on excised scalp tissue was conducted to evaluate the residual thermal damage of various laser parameters. RESULTS: The conventional micro- and minigrafts healed faster and resulted in better hair growth than the laser vaporization sites. The donor sites were judged to be comparable as far as healing, but more time consuming with the laser. The operative time for the laser recipient sites was 50% of that of the conventional sites. CONCLUSIONS: The clinical results of laser hair transplantation are very dependent upon the laser parameters and technique used. Though operative time may be significantly reduced, the end result clinically is dependent on proper choices of pulse parameters and technique.

Adult↗