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At least 415 records · Page 23Linked to original sources
PubMed2001

Extent of myocardial tissue damage during transmyocardial laser revascularization with the CO2 Heart Laser.

OBJECTIVE AND BACKGROUND: Transmyocardial laser revascularization (TMR) is the only surgical treatment for patients with severe diffuse coronary artery disease, who are not candidates for bypass grafting or percutaneous angioplasty. However, vaporization of tissue during the creation of channels leads to a certain loss of viable myocardium during every TMR procedure. METHODS: We analyzed serum levels of creatine kinase and creatine kinase MB subtype in 163 patients after sole TMR with a CO2 laser (wave length 10.6 microm, 800-watt power). The control group consisted of 35 consecutive CABG patients and 30 consecutive redo-CABG patients. Additionally, in the TMR group we measured echocardiographically the left ventricular ejection fraction before and after TMR. We recorded the total amount of laser energy applied, average and maximum energy per channel, and the number of created channels, in order to calculate the correlation between these parameters and postoperative enzyme levels or changes in the LVEF. RESULTS: After TMR, we measured higher creatine kinase levels compared to those in CABG patients (607.8+/-558.4 U/L vs. 285.0+/-292.3 U/L, p < 0.01). The relative proportion of CK-MB of total CK, however, was significantly lower after TMR, compared to that of the control group (4.5+/-3.0% vs. 10.1+/-6.4%, p < 0.01). Patients with a pronounced postoperative increase in CK-MB levels or a higher percentage of CK-MB of total CK also after TMR operations show a decline in left ventricular contractility. In the laser group, the maximum enzyme levels were detected significantly later than in the control group (25.0+/-19.4 h postoperatively vs. 8.7+/-9.1 h, p < 0.01). There was no significant correlation between the technical laser parameters or the number of created channels and the percentage of CK-MB of total CK or changes in left ventricular ejection fraction. CONCLUSIONS: CO2 laser TMR does not result in significant injury to the myocardium. Cardiac enzymes play an important role in the detection of perioperative myocardial infarction in TMR patients.

Carbon Dioxide↗
PubMed1992

A comparative analysis of adhesion reduction, tissue effects, and incising characteristics of electrosurgery, CO2 laser, and Nd:YAG laser at operative laparoscopy: an animal study.

In this study, the relative efficacy and tissue effects of lasers and electrosurgery at operative laparoscopy were evaluated. Thirty rabbits underwent surgical procedures to create extensive intraperitoneal adhesions. The animals were then randomly assigned to laparoscopic adhesiolysis utilizing either electrosurgery, CO2 laser, or Nd:YAG laser exclusively for the assigned group. Each surgical tool was utilized at its optimal power density to achieve the best results. The depth of thermal injury on ovarian and uterine tissues, and the speed at which various segments of the uterine horn were transected were also compared. All three modalities significantly reduced (p < 0.01) intraperitoneal adhesions by approximately 50%. The depth of thermal injury was threefold greater with the Nd:YAG laser than either electrosurgery or the CO2 at both ovarian and uterine tissues (p < 0.001). The speed of transection across the uterine horn was significantly slower (p < 0.001) with the Nd:YAG (2.6 +/- 0.3 sec) than either the CO2 laser (1.4 +/- 0.2 sec) or electrosurgery (1.5 +/- 0.2 sec). From this study, the authors conclude that the Nd:YAG laser causes more tissue damage and is less efficient at incising tissue than either CO2 or electrosurgery, but that all three modalities are equally effective for laparoscopic adhesiolysis.

Animals↗
PubMed1998

Histologic study of oral mucosa wound healing: a comparison of a 6.0- to 6.8-micrometer pulsed laser and a carbon dioxide laser.

Incisional wound healing in the canine oral mucosa was histologically monitored at 3, 7, and 14 days after incision. Healing was compared from a scalpel, a carbon dioxide (CO2) laser at 10.6 microm, and the Vanderbilt free-electron laser tuned to 6.0, 6.45, and 6.8 microm. A significant delay in wound healing was observed when incisions were made with the CO2 laser, probably attributable to the excess thermal damage caused by the continuous-wave laser beam. When using the short pulsed, free-electron laser, a much smaller delay comparable to the scalpel wound healing was observed. This smaller delay tended to decrease with increasing tissue absorption. The results emphasize the greater importance of laser pulse duration rather than wavelength in relation to the subsequent wound healing.

Absorption↗
PubMed1984

Treatment of cervical intraepithelial neoplasia with the CO2 laser: laser versus cryotherapy. A review of effectiveness and cost.

In the treatment of CIN, results of laser vaporization and those of cryotherapy have been comparable. Cryotherapy is much less expensive. It is techniquely easier to use and requires quieter, more reliable and less cumbersome equipment. Laser affords more precise tissue ablation, leaves less necrotic tissue, heals slightly faster, and may cause a transformation zone to move cephalad less frequently. Laser can be used for certain CIN lesions which cryotherapy would not cover. Patients frequently find laser less objectionable, when cost is not considered. At the present time, the expense of laser equipment does not seem warranted for the treatment of CIN alone. If laser equipment is available to the physician, it is as effective as other conservative modalities in the treatment of CIN and has applicability to a variety of vulvar and vaginal disorders not covered in this review.

Carbon Dioxide↗
PubMed2005

Digital simultaneous fluorescein and indocyanine green angiography, autofluorescence, and red-free imaging with a solid-state laser-based confocal scanning laser ophthalmoscope.

PURPOSE: To describe and to evaluate a novel confocal scanning laser ophthalmoscope (cSLO) for fluorescence angiography, fundus autofluorescence (FAF), and red-free imaging. METHODS: Digital infrared, red-free, FAF, fluorescein, and indocyanine green (ICG) angiography images were obtained with a cSLO in 766 patients. An optically pumped solid-state laser generates the excitation wavelength (488 nm) required for red-free, FAF, and fluorescein angiography images. For ICG angiography and infrared imaging, diode laser sources at 790 and 820 nm are used. Further features include an internal fixation control and a focus range of -24 to +30 diopters. RESULTS: High-image quality is achieved with a resolution of up to 5 microm per pixel in 30- x 30-degree images and allows for accurate delineation of normal and pathologic features. Simultaneous angiography offers high-contrast images. Corresponding display of quasi-simultaneous frames facilitates interpretation. A small focus difference between fluorescein and ICG scans occurs because of chromatic aberrations. Automated alignment and generation of mean images from several single frames allow for acquisition of high-resolution FAF images. CONCLUSION: Various laser-source related, optical, and electronic innovations improve cSLO fundus imaging for routine clinical application. A solid-state laser has advantages compared to argon gas laser sources, including less space occupation, heat emission, and noise production.

Adolescent↗
PubMed1992

Comparative histochemistry of port-wine stains after copper vapor laser (578 nm) and argon laser treatment.

The present study compared the histologic changes occurring 15 min after copper vapor laser (CVL; operating at 578 nm) and argon laser (488/514 nm) treatment of port-wine stains (PWS) over a range of energy densities (8-32 J/cm2) with corresponding pulse widths of 50-200 ms. Frozen tissue sections were stained with nitroblue tetrazolium chloride (NBTC). This histochemical method permits an accurate color differentiation between blue-stained viable and unstained thermally damaged cells. At 8, 10, and 12 J/cm2 the argon-laser injury was confined to epidermal cell layers; none to superficial dermal effects were found. Fluences of at least 15 J/cm2 produced a diffuse NBTC-negative coagulation necrosis. Exposure of PWS skin to 8-12 J/cm2 at 578 nm did not alter the integrity of epidermal cells. In the dermis, damage was confined to blood vessels and surrounding collagen, showing a clear demarcation from adjacent viable structures. The maximum penetration depth achieved with these vessel selective energy densities was 0.44 mm. At 15 J/cm2, besides vascular injury, damage to the basal cell layer also occurred. At fluences of 17-20 J/cm2 a diffuse necrosis similar to that induced by the argon laser was found. Vessel selectivity of the 578 nm wave band was achieved with pulse widths from 50-74 ms, exceeding the estimated "ideal" exposure time (0.1-10.0 ms) for a vascular selective laser effect. The NBTC method allowed identification of subtle laser-induced tissue changes providing accurate quantitative data relating to the extent of vascular injury.

Adult↗
PubMed1990

Dohi memorial lecture. Laser medicine and laser dermatology.

As laser devices become smaller, more reliable, and less expensive, dermatology will benefit from new laser-based therapeutic and diagnostic methods. Already there are simple, non-scarring, and relatively painless techniques for removal of pigmented lesions, tattoos, and vascular lesions. Because much of the basic and applied research in photobiology is grounded in dermatology research, dermatology will continue to be a major contributor to advances in laser medicine and photomedicine. An increase in understanding and ability to manipulate laser-tissue interactions will add greatly to the future of medicine and surgery, especially in applications utilizing pulsed lasers. We are learning how to: 1) vary wavelength, pulse duration, and energy to influence the nature of microscopic injury and host response in order to achieve a net therapeutic benefit; 2) utilize exogenous chromophores to increase the selection of targets for laser radiation; and 3) capture optical technology developed for industrial and military use, in order to benefit mankind with new medical and surgical techniques.

Animals↗
PubMed1993

Copper vapour laser treatment of port wine stains: clinical evaluation and comparison with conventional argon laser therapy.

The copper vapour laser (CVL), emitting at 578 nm, offers potential advantages over the argon laser in the treatment of port wine stains (PWS). In this study, two test areas were performed with each laser using a Hexascan delivery system in 31 patients with PWS. One area was treated at minimal blanching fluence and one at 75% of this fluence. The pulse width was constant for each patient (mean 155 ms). Four-month assessments were made using a fading scale of 0-4, and objectively by an index of light absorbence using reflectance spectrophotometry. The CVL-treated sites had significantly better fading scores than argon laser-treated sites at minimal blanching fluence (P < 0.005) and lower absorbence indices (P < 0.05). Fading was significantly greater at minimal blanching fluence than at 75% of this fluence by fading scores and absorbence index values for both lasers. Slight textural and pigmentary changes were seen in a small minority of both CVL and argon tests at minimal blanching fluence only. This study indicates that the CVL is superior to the argon laser in treatment of predominantly red-purple or purple PWS. The minimal blanching technique produces greater fading than a lower energy fluence.

Adolescent↗
PubMed2004

Efficacy of laser treatment of tattoos using lasers emitting wavelengths of 532 nm, 755 nm and 1064 nm.

BACKGROUND: Multifunctional laser devices can be used to treat tattoos successfully. OBJECTIVES: To report the efficacy of laser treatment in professional, amateur, accidental and permanent make-up tattoos from our own experience and to compare it with the literature. METHODS: We retrospectively studied 74 consecutive patients with professional, amateur, make-up and accidental tattoos between June 1998 and November 2000. Patients were treated with a Q-switched Nd:YAG laser (wavelengths of 532 nm and 1064 nm), a Q-switched alexandrite laser (755 nm) and a variable pulse Nd:YAG laser (532 nm). RESULTS: Fourteen patients (19%) achieved a complete response (>95% lightening of treated tattoos), 23 (31%) an excellent response (76-95% lightening) and 21 (28%) a good response (51-75% lightening). Sixteen patients (22%) showed only a slight improvement (< or =50% lightening). Make-up tattoos and blue-black professional tattoos were most successfully treated. Multicoloured professional tattoos needed more treatments (mean +/- SD 5.7 +/- 5.4) in comparison with single-colour tattoos (3.5 +/- 2.0). The amateur tattoos needed fewer treatments (2.8 +/- 1.1) in comparison with professional tattoos. With accidental tattoos the results depended on the particles which had penetrated the skin. In contrast to literature reports, newer tattoos showed a trend to better treatment results than older tattoos. CONCLUSIONS: Using modern Q-switched lasers, tattoos are removed successfully with minimal risk of scarring and permanent pigmentary alterations. Even multicoloured tattoos can be treated successfully and with a low rate of side-effects.

Adolescent↗
PubMed1997

Transurethral visual laser ablation of the prostate for benign prostatic hyperplasia using a KTP/YAG laser.

BACKGROUND: Transurethral visual laser ablation of the prostate (VLAP) has been established as an alternative method for the treatment of benign prostatic hyperplasia (BPH). However, most VLAP procedures utilize only a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Since a potassium-titenyl-phosphate (KTP) laser offers limited tissue penetration, KTP can be safely utilized to excise part of the obstructing prostatic tissue. This study assessed the interaction between KTP vaporization and YAG coagulative ablation to determine the safety and efficacy of VLAP utilizing a combined KTP/YAG treatment. METHODS: Forty patients with bladder outlet obstruction secondary to BPH were treated with VLAP using a KTP/YAG laser. The laser light was delivered by an angle delivery device. RESULTS: Most cases demonstrated a significant improvement in routine subjective and objective parameters (AUA symptom score, peak flow rate, average flow rate, and amount of residual urine). No significant complications relating to this procedure were reported, however, 4 patients experienced postoperative acute urinary retention. CONCLUSION: KTP/YAG laser ablation of the prostate is safe and effective for the treatment of BPH.

Aged↗
PubMed2003

Time-resolved microspectrofluorometry and fluorescence lifetime imaging of photosensitizers using picosecond pulsed diode lasers in laser scanning microscopes.

This work describes the time-resolved fluorescence characteristics of two different photosensitizers in single cells, in detail mTHPC and 5-ALA induced PPIX, which are currently clinically used in photodynamic therapy. The fluorescence lifetime of the drugs was determined in the cells from time-gated spectra as well as single photon counting, using a picosecond pulsed diode laser for fluorescence excitation. The diode laser, which emits pulses at 398 nm with 70 ps full width at half maximum duration, was coupled to a confocal laser scanning microscope. For time-resolved spectroscopy a setup consisting of a Czerny Turner spectrometer and a MCP-gated and -intensified CCD camera was used. Time-gated spectra within the cells were acquired by placing the laser beam in "spot scan" mode. In addition, a time-correlated single photon counting module was used to determine the fluorescence lifetime from single spots and to record lifetime images. The fluorescence lifetime of mTHPC decreased from 7.5 to 5.5 ns during incubation from 1 to 6 h. This decrease was probably attributed to enhanced formation of aggregates during incubation. Fluorescence lifetime imaging showed that longer lifetimes were correlated with accumulation in the cytoplasm in the neighborhood of the cell nucleus, whereas shorter lifetimes were found in the outer cytoplasm. For cells that were incubated with 5-ALA, a fluorescence lifetime of 7.4 ns was found for PPIX; a shorter lifetime at 3.6 ns was probably attributed to photoproducts and aggregates of PPIX. In contrast from fluorescence intensity images alone, different fluorescence species could not be distinguished. However, in the lifetime image a structured fluorescence distribution in the cytoplasm was correlated with the longer lifetime and probably coincides with mitochondria. In conclusion, picosecond diode lasers coupled to a laser scanning microscope equipped with appropriate detection units allows time-resolved spectroscopy and lifetime imaging with high spatial resolution and provides numerous possibilities in cellular and pharmaceutical research.

Animals↗
PubMedDate not supplied

Raman microspectrometry of laser-reshaped rabbit auricular cartilage: preliminary study on laser-induced cartilage mineralization.

Laser-assisted cartilage reshaping (LACR) is a relatively novel technique designed to noninvasively and permanently restructure cartilaginous tissue. It is believed that heat-induced stress relaxation, in which a temperature-mediated disruption of H2O binding is associated with conformational alterations in the proteoglycan and collagen-rich matrix, constitutes the underlying mechanism of LACR. Several reports have suggested that laser-mediated cartilage mineralization may contribute to the permanent shape change of laser-reshaped cartilage. In an effort to validate these results in the context of Er:glass LACR, we performed a preliminary Raman microspectrometric study to characterize the crystal deposits in laser-irradiated chondrocytes and extracellular matrix. For the first time, we identified intracellular calcium sulfate deposits and extracellular calcium phosphate (apatite) crystals in laser-reshaped rabbit auricular cartilage. Calcium carbonate deposits are localized in both irradiated and nonirradiated samples, suggesting that this mineral plays no role in conformational retention. In our discussion, we elaborate on the possible molecular and cellular mechanisms responsible for intra- and extracellular crystallization, and propose a novel hypothesis on the formation of apatite, inasmuch as the biological function of this mineral (providing structure and rigidity in bones and dental enamel) may be extrapolated to the permanent shape change of laser-irradiated cartilage.

Animals↗
PubMed1992

Comparison of infrared and helium-neon lasers in the measurement of blood flow in human skin by the laser-Doppler technique.

Histamine-induced changes in blood flow in normal human skin were assessed by laser-Doppler velocimetry using 2 lasers of different wavelengths: 780 nm infrared and 633 nm helium-neon. The visible flare response in skin was also measured by planimetry. Laser-Doppler velocimetry was shown to detect both the magnitude of the change in blood flow caused by histamine and also the extent of the changes in the skin. Both parameters were related to the dose of histamine, which ranged between 25 and 750 pmol/site. There was good correlation between the magnitude of the histamine-induced blood flow change and the extent of the response. The flare induced by histamine and measured by planimetry was similar in extent to the blood flow change recorded by laser-Doppler velocimetry. No difference in either the magnitude or the extent of blood flow changes in response to histamine, as measured by laser-Doppler velocimetry, were found when lasers of different wavelengths were used.

Adult↗
PubMed1988

Laser-assisted vasovasostomy in the rat. Comparison of CO2 and neodymium:YAG laser techniques.

A comparative study was undertaken to investigate the Nd:YAG and CO2 laser systems for laser-assisted vasovasostomies (LAVs). In 32 rats 64 vasovasostomies were performed, either conventionally sutured (CSV) or laser-welded (LAV-CO2 and LAV-Nd:YAG). Postoperative investigations included patency tests, gross examination, light and electron microscopy. The highest rate of sperm granulomas (50%) and the lowest patency rate (50%) was seen in the LAV-Nd:YAG group. LAV-CO2 showed the lowest rate of sperm granulomas (12.5%) and had a patency rate (82%) which was comparable to that of CSV (88%). Laser-assisted vas anastomosis is time saving and technically easy to perform. Contrary to microvascular anastomoses, where both laser types offer the same results, vas anastomosis is better done using a CO2 laser system.

Animals↗
PubMed1991

Alternation of the q-switched Nd:YAG laser and the cw argon laser for tunneling through organic material.

The rapidly alternating combination of Nd:YAG laser power of the optical break-down mode with cw energy of the argon laser ablates tissue. Blood agar provides a standard test medium as tissue substitute and permits to quantify the effect of various laser energy combinations to achieve optimal ablation. High wattage of the Nd:YAG laser provides destructive pressure that creates fissures which act as the light traps of a black body simulator for efficient cw argon laser energy conversion to pressure and kinetic energy. Within the fissure the deposited cw argon laser energy is directed by gradients toward the tissue surface so that deepening troughs or tunnels are formed by expelling tissue debris.

Agar↗
PubMed1992

UV lasers for flow cytometric analysis: HeCd versus argon laser excitation.

Applying flow cytometric single cell analysis, we compared the performance of UV excitation from argon ion and HeCd lasers using various UV-excitable fluorochromes of cell kinetic and cell physiological relevance. The AT-specific DNA fluorochromes DAPI, Hoechst 33258, and Hoechst 33342 showed no significant differences of G1-phase resolution and cell cycle distribution. With the HeCd laser, high-resolution cell kinetic analysis applying the novel BrdU/Hoechst-PI quenching technique showed superior resolution and an almost normalized G2M/G1 channel ratio of the first cell cycle. Indo-1 analysis for detection of intracellular free calcium gave similar results for both excitation sources, although the indo-1 ratio of activated cells was lower for HeCd excitation. Monochlorobimane as an indicator fluorochrome of glutathione content could not be excited sufficiently with the 325-nm line of the HeCd laser and exhibited poor resolution between positive and negative cells. However, the second glutathione-specific fluorochrome o-phtalaldehyde gave even better results with the HeCd laser. Our data indicate that air-cooled HeCd lasers are cheap and reliable UV-excitation sources for most UV-excitable fluorochromes, and might be an alternative to the expensive water-cooled argon and krypton laser.

Argon↗
PubMed1999

Photodynamic therapy of atherosclerosis using YAG-OPO laser and Porfimer sodium, and comparison with using argon-dye laser.

We performed photodynamic therapy (PDT) using the Yttrium Aluminium Garnet-Optical Parametric Oscillated (YAG-OPO) laser in cases of atherosclerosis, and examined its efficacy in vivo. We also performed PDT using an Argon-dye (Ar-dye) laser with the same output, and compared the efficacies. Following balloon denudation injury of the thoracoabdominal aorta, rabbits were raised on a cholesterol diet for 16 weeks, producing atheroma in that region. At 24 h following the administration of Photofrin 5 mg/kg, PDT was performed, and animals were sacrificed at 1 day, 1 week, and 2 weeks following the procedure to examine its efficacy. This was compared with the efficacy of PDT using the Ar-dye laser. Following PDT using a YAG-OPO laser, an increase in the vessel lumen was seen due to reduction of the hypertrophic intima and media, without the appearance of inflammatory cells. This result was seen more strongly in PDT using the pulse wave YAG-OPO laser than with the continuous wave Ar-dye laser, affecting not just the intima but also the media. These data demonstrated that PDT can effectively regress atherosclerotic lesions.

Animals↗
PubMed2003

Chemical imaging using microline laser ablation: performance comparison of Gaussian and flat top lasers.

In previous studies, the potential of a microline imaging arrangement for surface characterization of solid samples in air at atmospheric pressure using laser-induced plasma spectrometry (LIPS) has been demonstrated. An improvement of this approach to obtain a uniform ablation along the microline focus that leads to a representative spatial distribution of elements on the sample surface is presented. For this purpose, the influence of beam energy distribution of two types of Nd:YAG pulsed lasers (a Gaussian laser and a flat top laser) on lateral resolution, intensity profiles of elements, chemical distribution maps, and plasma electron temperature has been investigated. As models of homogeneous and compositionally patterned samples, a stainless steel sample and a photovoltaic cell were chosen for this study. The results demonstrated that the Gaussian laser provides the best lateral resolution, but more redeposition at both sides of the microline crater, while the chemical maps obtained with the flat top laser matched with the distribution of the constituents of the sample surface.

Energy-Generating Resources↗