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At least 199 records · Page 11Linked to original sources
PubMed1994

Experimental laser anastomosis of the colon. Long-term results and histologic findings after laser closure of colotomies.

PURPOSE: Our previous experimental work showed the feasibility of colon anastomosis using laser; however, it also revealed a narrowing tendency after laser anastomosis. Long-term observation of the postoperative course of laser anastomosis was planned to assess this point. METHODS: Clinical observation and histologic examination of transverse colotomies (average, 21.2 mm) in New Zealand white rabbits (n = 12) closed with a 1,064-nm neodymiumyttrium aluminum garnet (Nd:YAG) laser were carried out up to the third postoperative month, compared with closure of colotomies using a single layer of interrupted sutures of 5-0 Maxon (Davis & Geck, Pearl River, NY) in a control group (n = 12). RESULTS: Whereas the narrowing tendency was observed up to one month after the operation in the laser group (P < 0.05), it disappeared at three months following the operation without causing abnormal weight loss during the experiment. Simultaneously, there was again a marked decrease in adhesion formation following laser anastomosis (P < 0.01). Collagen fibers were observed earlier in the laser group. CONCLUSIONS: An earlier commencement of collagen synthesis after laser anastomosis was proved. A narrowing tendency, which was observed from seven days to one month postoperatively, disappeared at three months after laser anastomosis without exerting any effect on growth.

Anastomosis, Surgical↗
PubMed1991

Laser irradiation and Raman spectroscopy of single living cells and chromosomes: sample degradation occurs with 514.5 nm but not with 660 nm laser light.

In Raman spectroscopic measurements of single cells (human lymphocytes) and chromosomes, using a newly developed confocal Raman microspectrometer and a laser excitation wavelength of 514.5 nm, degradation of the biological objects was observed. In the experiments high power microscope objectives were used, focusing the laser beam into a spot approximately 0.5 micron in diameter. At the position of the laser focus a paling of the samples became visible even when the laser power on the sample was reduced to less than 1 mW. This was accompanied by a gradual decrease in the intensity of the Raman signal. With 5 mW of laser power the events became noticeable after a period of time in the order of minutes. It is shown that a number of potential mechanisms, such as excessive sample heating due to absorption of laser light, multiple photon absorption, and substrate heating are unlikely to play a role. In experiments with DNA solutions and histone protein solutions no evidence of photo damage was found using laser powers up to 25 mW. No degradation of cells and chromosomes occurs when laser light of 660 nm is used. The most plausible explanation therefore seems to be that the sample degradation is the result of photochemical reactions initiated by laser excitation at 514.5 nm of as yet unidentified sensitizer molecules or complexes present in chromosomes and cells but not in purified DNA and histone protein samples.

Animals↗
PubMed1993

Coronary artery perforation during excimer laser coronary angioplasty. The percutaneous Excimer Laser Coronary Angioplasty Registry.

OBJECTIVES: The aim of this study was to analyze the risk of vessel perforation during excimer laser angioplasty. BACKGROUND: Vessel perforation is a serious complication of angioplasty. METHODS: A total of 764 patients had 858 stenoses treated with excimer laser angioplasty. Laser catheters had a diameter of 1.4, 1.7 or 2 mm. Laser energy was delivered in pulses of 135 ns, at a frequency of 25 s-1 and at a fluence of 30 to 60 mJ/mm2. Follow-up angiography was requested for all patients who did not require emergency bypass surgery. RESULTS: In the 764 consecutive patients treated with excimer laser coronary angioplasty, vessel perforation occurred in 23 patients (3%). Nine patients had a major complication resulting directly from vessel perforation (cardiac tamponade, myocardial infarction or need for bypass surgery) and 14 had no clinical complications after successful sealing of the puncture site. No patient with a perforation died. Multivariate analysis showed that bifurcation lesions (odds ratio [OR] = 3.5; p = 0.049), diabetes mellitus (OR = 3.15; p = 0.029) and female gender (OR = 2.86; p = 0.013) were associated with an increased risk of vessel perforation. Lesions > 10 mm in length (OR = 0.45; p = 0.206), calcified stenoses (OR = 0.26; p = 0.088) and saphenous vein graft lesions (OR = 0.50; p = 0.295) were not at increased risk. Vessel perforation was seen in 10 (8.3%) of 120 lesions in which the laser catheter was equivalent in diameter to the target vessel (< or = 0.5 mm smaller in size) but in only 8 (1.5%) of 525 lesions in which the laser catheter was > 1 mm smaller than the target vessel (p = 0.001). CONCLUSIONS: Most lesions thought to be suitable for excimer laser treatment are not at increased risk of perforation. The complication may be avoided by improved patient and laser catheter size selection.

Adult↗
PubMed2004

Automated laser registration in image-guided surgery: evaluation of the correlation between laser scan resolution and navigation accuracy.

Markerless patient registration based on the facial skin surface makes logistics prior to image-guided surgery much easier, as it is not necessary to place and measure registration markers. A laser scan registration of the surgical site takes the place of conventional marker-based registration. In a clinical study, the stability and accuracy of markerless patient registration was evaluated in 12 patients. Intraoral titanium markers served as targets for the infrared-pointer of the navigation system in order to check the accuracy of the markerless registration process. The correlation between laser scan resolution and navigation accuracy was checked using seven different laser scan resolutions (a cloud of 300,000 laser scan points down to 3750 laser scan points of the surgical site). The markerless patient registration was successful as long as high laser scan resolution was used (30,000 laser scan points and more): the titanium markers were detected with a mean deviation of 1.1 +/- 0.2 mm. Low resolution laser scans (6000 laser scan points of the surgical site and less) revealed inaccuracies up to 6 mm.

Humans↗
PubMed2003

Argon laser vs. subthreshold infrared (810-nm) diode laser macular grid photocoagulation in nonexudative age-related macular degeneration.

BACKGROUND: A diode laser can be used to create a subthreshold (invisible end point) lesion in patients with age-related macular degeneration (AMD). This has the potential benefit of localizing the treatment effect to the retinal pigment epithelium and sparing more of the overlying sensory retina. We performed a study to compare the safety and efficacy of argon laser and subthreshold infrared (810-nm) diode laser macular grid photocoagulation in reducing the number of drusen in patients with AMD. METHODS: We reviewed the charts of 144 patients with bilateral early-stage nonexudative AMD, characterized by soft drusen. One eye of each patient was treated, and the other eye served as a control. Seventy-eight eyes of 78 patients with a mean age of 67.5 (standard deviation [SD] 8.3) years underwent argon laser macular grid photocoagulation at a university-affiliated hospital in Bologna, Italy, and 66 eyes of 66 patients with a mean age of 66.4 (SD 6.3) years underwent subthreshold infrared (810-nm) diode laser macular grid photocoagulation at a private clinic in Bologna. Each group was classified into three subgroups based on the number of drusen (more than 20, 10 to 20, or less than 10). The patients underwent fluorescein angiography, fundus examination, measurement of far (Snellen chart) and near (Jaeger chart) best corrected visual acuity, and visual field and contrast sensitivity testing. The mean length of follow-up was 18 (SD 0.5) months. RESULTS: At 18 months, far and near best corrected visual acuity were statistically significantly improved in the treatment groups compared with the untreated group (p < 0.001, Mann-Whitney U test). There was no significant difference in visual acuity between the treatment groups. Compared with baseline, the number of drusen was significantly reduced in both treatment groups (p < 0.001). Evolution of the disease was observed in the untreated group. The visual field was slightly but significantly reduced after argon laser treatment (p < 0.001) but not diode laser treatment; the difference in visual field between the two groups was not significant. There was a slight reduction in contrast sensitivity, particularly with night vision, after argon laser treatment but not diode laser treatment. The difference between the two treatment groups was significant (p < 0.01). INTERPRETATION: Subthreshold infrared diode macular grid photocoagulation may be a safe and viable method for preventing progression of nonexudative AMD.

Aged↗
PubMed2000

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: compositional, structural, and phase changes of DP-bioglass paste after irradiation by CO2 laser.

Nowadays, fractured teeth are difficult to treat effectively. Currently, root fractures are usually treated by root amputation, hemisection or tooth extraction. If the fusion of tooth fracture by laser were possible, it would offer a different therapy to repair fracture teeth. We tried to use a developed DP-bioactive glass paste to fuse or bridge the tooth crack line by a medium energy continuous-wave CO2 laser. The study is divided into three parts: (1) The compositional and structure changes in tooth enamel and dentin after laser treatment; (2) The phase transformation and recrystallization of DP-bioactive paste during exposure to the CO2 laser; (3) The thermal interactions and bridge mechanism between DP-bioactive glass paste and enamel/dentin when they are subjected to CO2 laser. The present report will focus on the second part that will examine the changes of laser-exposed DP-bioactive glass paste by means of X-ray diffractometer (XRD), Fourier transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). From the study, we could find that the temperature increase due to laser irradiation is greater than 900 degrees C and that the DP-bioactive glass paste could be melted in a short period of time after irradiation. In the study, we successfully developed a DP-bioactive glass paste which could form a melting glass within seconds after exposure to a medium energy density continuous-wave CO2 laser. The paste will be used in the near future to bridge the enamel or dentin surface crack by the continuous-wave CO2 laser.

Carbon Dioxide↗
PubMed2002

Modulation of trigeminal laser evoked potentials and laser silent periods by homotopical experimental pain.

Cutaneous laser stimulation activates predominantly the A-delta and C mechano-heat nociceptors. Applied to the perioral region, low intensity CO(2)-laser pulses evoke reproducible trigeminal cortical evoked potentials (LEPs). High intensity CO(2)-laser stimuli induce a reflex response in the contracted jaw-closing muscle, the so-called laser silent period (LSP). Both LEPs and LSP provide a useful tool to study the physiology of the trigeminal nociceptive system. In ten healthy subjects we recorded the subjective ratings of the perioral laser stimulation and the trigeminal LEPs and LSP before, during and after homotopic experimental tonic muscle (infusion of hypertonic saline into the masseter muscle) and tonic skin pain (topical application of capsaicin to the cheek). LEPs were recorded from the vertex at two stimulus intensities: low (1.1 x pain threshold, PTh) and high (1.5 x PTh). LSP from masseter and temporalis muscles were recorded bilaterally through surface electromyographic (EMG) electrodes. CO(2)-laser pulses were applied to the perioral region (V2/V3) on the painful and non-painful side. The amplitude of LEPs increased with higher stimulus intensities (P<0.0001), but were suppressed by 42.3+/-5.3% during experimental muscle pain (P<0.0001) and by 41.6+/-3.2% during skin pain (P<0.0001). No pain-related effects were observed for the N and P latency of the LEPs (P> 0.20). The LSP in the masseter and temporalis muscles had similar onset-latency (80+/-5 ms), offset-latency (111+/-5 ms) and duration (31+/-4 ms). Experimental pain had no effect on the onset- and offset-latency (P>0.05). Experimental pain, whether from muscle or from skin, reduced the degree of suppression (P<0.01) and the area under the EMG curve (P< 0.005) of the LSP. The LSP was still suppressed during the post-pain recordings when the skin pain had disappeared (P<0.05). In all experiments experimental tonic pain decreased the subjective ratings of the perioral laser stimulation (P< 0.001). Experimental tonic pain, either from muscle or from skin, induced bilateral inhibitory effects on the trigeminal laser evoked potentials and brainstem reflex responses and on the subjective ratings of the laser pulses. These effects could be mediated through the activation of segmental and suprasegmental inhibitory systems that may function interdependently.

Administration, Topical↗
PubMed1997

Prospective, randomized, multicenter comparison of laser-facilitated balloon angioplasty versus stand-alone balloon angioplasty in patients with obstructive coronary artery disease. The Laser Angioplasty Versus Angioplasty (LAVA) Trial Investigators.

OBJECTIVES: The goal of this study was to examine the relative safety and efficacy of laser-facilitated percutaneous transluminal coronary angioplasty (PTCA) versus "stand-alone" PTCA. BACKGROUND: Plaque debulking with lasing before PTCA may result in improved lumen dimensions and decreased rates of periprocedural ischemic complications, thus improving short- and long-term outcomes after percutaneous intervention. The mid-infrared holmium:yttrium-aluminum-garnet (YAG) laser has been shown to be effective in a variety of plaque subtypes and may be particularly useful in high risk acute ischemic syndromes. METHODS: A total of 215 patients (mean [+/-SD] age 61 +/- 12 years) with 244 lesions were prospectively randomized at 14 clinical centers to laser versus stand-alone PTCA. After laser treatment, all patients underwent PTCA; 148 patients (69%) had unstable angina. RESULTS: The procedural success rate without major catheterization laboratory complications was similar in patients assigned to laser treatment or PTCA alone (96.6% vs. 96.9%, p = 0.88), as was the in-hospital clinical success rate (89.7% vs. 93.9%, p = 0.27). There was no difference in postprocedural diameter stenosis after laser treatment compared with PTCA (18.3% +/- 13.6% vs. 19.5% +/- 15.1%, p = 0.50). However, use of the laser, versus PTCA alone, did result in significantly more major and minor procedural complications (18.0% vs. 3.1%, p = 0.0004), myocardial infarctions (4.3% vs. 0%, p = 0.04) and total in-hospital major adverse events (103% vs. 4.1%, p = 0.08). At a mean follow-up time of 11.2 +/- 7.7 months, there were no differences in late or event-free survival in patients assigned to laser treatment versus PTCA alone. CONCLUSIONS: Compared with stand-alone PTCA, laser-facilitated PTCA results in a more complicated hospital course, without immediate or long-term benefits.

Angioplasty, Balloon, Coronary↗
PubMed2006

Adjustable fragmentation in laser desorption/ionization from laser-induced silicon microcolumn arrays.

Laser-induced silicon microcolumn arrays (LISMA) were developed as matrix-free substrates for soft laser desorption/ionization mass spectrometry (SLDI-MS). When low-resistivity silicon wafers were irradiated in air, sulfur hexafluoride, or water environment with multiple pulses from a 3 x omega mode-locked Nd:YAG laser, columnar structures were formed on the surface. The radii of curvature of the column tips varied with the processing environment, ranging from approximately 120 nm in water, to <1 mum in SF6, and to approximately 2 mum in air. In turn, these microcolumn arrays were used as matrix-free soft laser desorption substrates. In SLDI-MS experiments with a nitrogen laser, the microcolumn arrays obtained in water environment readily produced molecular ions for peptides and synthetic polymers at low laser fluence. These surfaces demonstrated the best ion yield among the three arrays. The threshold laser fluence and ion yield were comparable to those observed in matrix-assisted laser desorption/ionization. Low-femtomole sensitivity and approximately 6000 Da mass range were achieved. At elevated laser fluence, efficient in-source decay was observed and extensive peptide sequence information was extracted from the resulting mass spectra. The versatility of LISMA was attributed to confinement effects due to the submicrometer morphology and to the surface, thermal, and optical properties of processed silicon.

Silicon↗
PubMed2001

Laser hair removal with alexandrite versus diode laser using four treatment sessions: 1-year results.

BACKGROUND: Laser hair removal is the treatment of choice for hypertrichosis. The two most commonly used hair removal lasers are compared. OBJECTIVE: To present the results of a comparative study examining the role of wavelength, fluence, spot size, pulse width, and cooling systems on long-term results after a series of four laser hair removal treatments using the 755 nm alexandrite and 800-810 nm diode lasers. METHODS: The axillae of 15 untanned, type I-V patients were treated side by side four times at 4- to 6-week intervals with a 755 nm, 3-msec pulse width, cryogen spray-equipped alexandrite laser and an 800 nm, variable pulse width, cooled sapphire window-equipped diode laser. Each patient was pretested and treated with the maximum fluence tolerated at the largest spot size available for each laser (12 mm round/113 mm2 for the alexandrite and 9 mm for the diode). RESULTS: Evaluations were done at 3, 6, 9, and 12 months after the last treatment. Twelve-month results with the alexandrite and diode lasers achieved 85% versus 84% hair reduction. The fact that tan avoidance was strictly followed permitted the use of relatively high fluences (25-30+ J/cm(2)) even in type IV patients. For most patients, four treatment sessions using high fluences (30-40 J/cm(2)) with relatively large spot sizes (12 mm round for the 755 nm alexandrite and 9 mm for the 800 nm diode) resulted in 12-month hair reductions in the 90% range. CONCLUSION: Both the alexandrite and diode lasers in this 12-month study produced excellent long-term hair reductions.

Adult↗
PubMed1992

[Treatment of hemangioma with the neodymium:yttrium-aluminum-garnet laser (Nd:YAG laser)].

Laser therapy and in particular Nd:YAG laser therapy has become of increasing importance amongst the various methods of treating haemangiomas. Nd:YAG laser radiation penetrates deep into the tissue. To avoid undesirable results of treatment, certain treatment guidelines must be observed: to protect the tissue from serious heat damage, the Nd:YAG laser radiation should be applied exclusively with simultaneous tissue cooling. Depending on the location of the haemangioma, this is carried out with ice cubes (if possible, not containing air bubbles) or with an ice-cold Ringer solution. The depth of penetration of the laser radiation can be increased by tissue compression with a piece of ice or with a special glass disc. In very voluminous haemangiomas, the laser light is additionally applied via a bare fibre directly on to the vascular tissue. The laser power densities we use are between 500 and 3,000 watts/cm2. The power chosen depends on the tissue effect of the laser radiation. Blanching of the vascular tissue without carbonisation is aimed at. With consistent observance of the treatment guidelines specified, haemangiomas should be treated as early as possible with the Nd:YAG laser. The treatment principle of "wait and see" is often advocated, but we consider to be obsolete, since cosmetically and functionally unsatisfactory residual scars may remain even after complete haemangioma regression. Moreover, the progressive haemangiomas which often lead to complications cannot be distinguished from regressive haemangiomas. Last but not least, the child and the parents should be spared the (in some cases appreciable) psychological strain of a haemangioma.

Adolescent↗
PubMed2002

Endovenous treatment of the greater saphenous vein with a 940-nm diode laser: thrombotic occlusion after endoluminal thermal damage by laser-generated steam bubbles.

PURPOSE: Despite a rapid spread of the technique, very little is known about the laser-tissue interaction in endovenous laser treatment (EVLT). We evaluated EVLT of the incompetent greater saphenous vein (GSV) for efficacy, treatment-related adverse effects, and putative mechanisms of action. METHODS: Twenty-six patients with 31 limbs of clinical stages C(2-6), E(P), A(S,P), P(R) with incompetent GSV proven by means of duplex scanning were selected for EVLT in an outpatient setting. A 600-microm fiber was entered into the GSV via an 18-gauge needle below the knee and proceeded to the saphenofemoral junction (SFJ). After infiltration of tumescent local anesthesia, multiple laser pulses of 15 J energy and a wavelength of 940 nm were administered along the vein in a standardized fashion. D-dimers were determined in peripheral blood samples 30 minutes after completion of EVLT in 16 patients and on postoperative day 1 in 20 patients. One GSV that was surgically removed after EVLT was examined by means of histopathology. Additionally, an experimental in vitro set-up was constructed as a means of investigating the mechanism of laser action within a blood-filled tube. RESULTS: A median of 80 laser pulses (range, 22-116 laser pulses) were applied along the treated veins. On days 1, 7, and 28, all limbs except one (97%) showed a thrombotically occluded GSV. In one patient, the vessel showed incomplete occlusion. The distance of the proximal end of the thrombus to the SFJ was a median 1.1 cm (range, 0.2-5.9 cm) in the remaining patients. Adverse effects in all 26 patients were ecchymoses and palpable induration along the thrombotically occluded GSV that lasted for 2 to 3 weeks. In two limbs (6%), thrombophlebitis of a varicose tributary required oral treatment with diclofenac. D-dimers in peripheral blood were tested with normal results in 14 of 16 patients 30 minutes after completion of the procedure and elevated results in 7 of 20 patients at day 1 after EVLT. However, an increase of D-dimers from day 0 to day 1 was observed in 15 of the 16 patients undergoing tests 30 minutes after EVLT and on day 1. The 940-nm laser was demonstrated by means of in vitro experiments and the histopathological examination of one explanted GSV to act by means of indirect heat damage of the inner vein wall. CONCLUSION: EVLT of the GSV with a 940-nm diode laser is effective in inducing thrombotic vessel occlusion and is associated with only minor adverse effects. Laser-induced indirect local heat injury of the inner vein wall by steam bubbles originating from boiling blood is proposed as the pathophysiological mechanism of action of EVLT.

Female↗
PubMed1999

Computer-guided laser probe for ablation of brain tumours with ultrashort laser pulses.

A computer-guided laser probe has been developed for the application of ultrashort-pulsed lasers in neurosurgery. It is part of a novel operation concept for the treatment of deep-seated brain tumours. The system combines the positioning accuracy of stereotactic or neuronavigated instruments with the precise and therefore gentle characteristics of surgical lasers. The probe has an outer diameter of 5.5 mm and is directly inserted into the target volume. By a synchronized movement of three coaxial tubes, which guide the embedded optics, the laser radiation is focused at any time onto the current tissue surface. Since every single laser pulse has only a small effective volume of about 8 x 10(5) microm3, the application of a large number of succeeding pulses can be adapted to required geometries. Tissue fragments are removed from the growing operation cavity by continuous irrigation and suction through the laser probe. Blood vessels are detected by a confocal laser-scanning microscope, which is integrated into the probe, and can be closed by an additional coagulating laser. In this paper, the design and technical properties of the laser probe as well as its use in ablation and coagulation experiments are presented. A description of the overall operation system is given.

Animals↗
PubMed1998

Principles and applications of laser lithotripsy: experience with the holmium laser lithotrite.

INTRODUCTION AND OBJECTIVES: The initial clinical experience with holmium laser energy applied for endoscopic lithotripsy was positive. The current study is presented as a contrast to the preliminary findings and as a means of defining the clinical usefulness of this specific laser lithotrite. MATERIALS AND METHODS: Calculi were treated endoscopically with the holmium laser lithotriptor and data was gathered prospectively. The youngest patient in the series was a thirteen-month--old who underwent percutaneous therapy, while the youngest patient on whom a retrograde endoscopic procedure was performed was a six-year old male patient with a proximal ureteral calculus. Lower water density, quartz fibers delivery systems were developed and employed. Fiber diameters ranged from 200-1000 micrograms. The smaller fibers were employed most commonly through the actively deflectable, flexible endoscope to facilitate treatment with maximum deflection. Larger fibers, with their much larger vaporization bubbles, were used through rigid endoscopes to debulk large stone burdens. RESULTS: A total of 210 patients with 249 calculi were treated. All major stone compositions were treated with minimal variation in laser efficiency. All but three of 109 ureteral calculi were treated in a retrograde fashion to completion (i.e., "stone free") in one sitting (97%). One-hundred thirteen renal stone burdens were treated with the holmium laser; 99 of these were treated solely in a retrograde fashion. Of the latter, 79 (80%) required only a single session. The combination of the actively deflectable, flexible ureteroscope and the 200-micrograms fiber facilitated treatment to completion of 38 to 45 lower-pole caliceal calculi (85%). The success of ureteropyeloscopic lithotripsy with the holmium laser for all intrarenal calculi, including staged or second sitting for large complex stone burdens, was 90%. Sixteen percutaneous procedures (13 renal and 3 ureteral calculi) employed the holmium laser as an endoscopic lithotrite. All 28 patients with large bladder calculi with a mean diameter of 41.8 mm were treated to completion in one sitting. Complications from holmium laser energy, including postoperative ureteral stricture disease, were not encountered in this series. CONCLUSIONS: Holmium laser energy is uniquely suited to treat urinary calculi safely regardless of stone size, location, or metabolic composition, and has particular efficacy in complex clinical presentations.

Child↗
PubMed2000

Thermal lesions produced by CO2 laser beams: new findings to improve the quality of minimally invasive and transmyocardial laser revascularization protocols.

OBJECTIVE: The objective of this study was to investigate the possible existence of a set of critical combinations among medical CO2 laser device set-ups and to compare the resigns of diameter and depth of irradiated tissue. These data are useful to the surgeon to identify a general operative protocol that allows both to forecast the beam behavior on a large variety of operative conditions accurately and to identify the related safety margins. Two methods have been addressed: the more traditional free-air beam delivery to the tissue and the more modern requirements of the minimally invasive surgery concepts, which use fiberoptic-based delivery systems for the CO2 laser beam. BACKGROUND DATA: In the past many articles have been written about the interaction between laser beams and biological media. However, the CO2 laser beam at 10.6 microm has always challenged research institutions and manufacturers to find the ideal combinations between a suitable fiberoptic-based delivery system concept and the injury threshold conditions recommended for minimally invasive surgery (MIS) and transmyocardial laser revascularization (TMLR) applications. One of the main challenges is to deliver the radiation at 10.6 microm without serious damage to the fiberoptic-based scalpel and the irradiated tissue by the burn of the fiber in use. METHODS: Five rabbits weighing 3 to 3.5 kg were sacrificed and 60 samples of trachea, myocardium, aorta, and esophagus were immediately excised, trimmed free of the adherent connective tissue, and irradiated in the intima portion of the wall. A commercial TEM medical CO2 laser was coupled to a silver halide fiber (0.9 mm in diameter) and subsequently to regular focusing heads (2.5-inch and 5-inch focal length) for pulsed laser beam delivery. The parameters chosen were: 33, 50, 65, and 100 mJ per pulse, 10 and 20 ms pulse width, delivered in two sets of experiments, one with all the pulsed beam frequencies below 5 Hz, the other between 15 Hz and 20 Hz. The same tests were conducted on 10 blocks of 3 different plastic types to simulate in one single procedure the laser radiation in responses to both hard, low-water content tissues such as bone and of common plastic compounds (such as polymethylmethacrylates [PMMA]) routinely used in orthopedic surgery. An optical microscope was used to measure all the lesions (diameter and depth in millimeters) in all the samples and to identify the smallest and the largest one against which similar thermal injuries found on the other media were compared. RESULTS: This study demonstrates that for power densities between about 520 and 790 W/cm2 per pulse achieved with the silver halide fiber generated a minimal lesion on the myocardium and aortic tissues. This can be used as reference threshold for MIS and TMLR. The minimal injury threshold on PMMA has been reached at 393 W/cm2 per pulse at 1 Hz. This approached the conditions of a pulsed beam delivered in air on the same medium via a focal spot of an 8.7 inch focal. Surprisingly, all the treated media show lesions that follow similar patterns within a well-defined and limited range of both diameter and depth. This effect was obtained by using power densities ranging from 393 to 6310 W/cm2 per pulse regardless of all the other parameters, including power delivery method, the type of irradiated tissue and the frequency between 0 and 20 Hz. Only the combination power density-type of tissue appears to be decisive. The geometrical convergence of the diameter shows a much smoother pattern than the one of the depth, due to two different irradiation modalities. CONCLUSIONS: The selection of the CO2 laser beam parameters and the irradiated media reported in this article have allowed identification of a critical set of ablative conditions to be further used in the operating room.

Animals↗
PubMed2002

Effectiveness of the normal-mode ruby laser and the combined (normal-mode plus q-switched) ruby laser in the treatment of congenital melanocytic nevi: a comparative study.

The effect of the normal-mode ruby laser (NMRL) and the combined (normal mode plus Q-switched) ruby laser on congenital melanocytic nevi (CMN) was evaluated, and the degree to which both laser treatment regimens remove melanocytes was compared in 15 patients. Each nevus was marked to designate half of the lesion for the NMRL treatment and half of the lesion for combined ruby laser treatment. The efficacy of each laser treatment was correlated with the degree of clinical improvement determined by photographic assessment, histological examination, and melanin reflectance spectrometry before and 3 months after laser treatment. A single treatment using the NMRL with energy fluences of both 20 J per square centimeter and 30 J per square centimeter resulted in a slight, but not significant, improvement in lightening of pigmentation (42.61% and 30.38%, respectively). A better clinical response (excellent to good) and higher percentage of lightening (64.45%-72.43%) was noted in the combined ruby laser-treated areas than the NMRL-treated areas. Histological results showed that the combined ruby laser provided a marked decrease in the number of the nevomelanocytic nests in both the junctional area and the papillary and reticular dermis, whereas the NMRL (with energy fluences of either 20 J per square centimeter or 30 J per square centimeter) caused a decrease in the junctional area and the papillary dermis. None of the nevi had complete clearance of the pigmentation after a single treatment. Therefore, multiple (four to five) treatment sessions are needed to cause complete removal of nevomelanocytic nests in CMN. In conclusion, the combined ruby laser is more effective than the NMRL alone in the treatment of CMN without scarring or textural change of the skin.

Adolescent↗
PubMed1975

Clinical evaluation of the carbon dioxide laser for burn wound excisions: a comparison of the laser, scalpel, and electrocautery.

The use of a 100 watt carbon dioxide laser for surgical excisions of burn eschar was evaluated in 13 patients with symmetrical burns. In each patient, laser excision was compared with either scalpel or electrocautery excision of a comparable area. Graft "take," blood loss, and operative speed were measured. Graft "take" following laser excisions was comparable to that obtained when either scalpel or electrocautery was used. Regression analysis indicates that laser excisions involved 29% of the blood loss encountered with scalpel excisions and that laser speed was 1.49 times scalpel speed. Although laser blood loss was 60% of electrocautery blood loss, laser speed was significantly slower: 73% of electrocautery speed. These differences, however, were of small clinical consequence. It is felt that the surgical arm of this laser is at present quite awkward and is in need of technological refinement if the full potential of the laser is to be realized.

Burns↗
PubMed2005

Effect of laser and environmental parameters on reducing microbial contamination of stainless steel surfaces with Nd:YAG laser irradiation.

AIMS: The effect of laser (pulse repetition frequency, pulse energy and exposure time) and environmental parameters (pH, NaCl concentration and wet or dry samples) of Nd:YAG laser decontamination of stainless steel inoculated with Escherichia coli, Staphylococcus aureus and Listeria monocytogenes was investigated. METHODS AND RESULTS: Stainless steel discs were inoculated with the bacterial samples and exposed to laser energy densities to about 900 J cm(-2). These inactivation curves allowed selection of laser parameters for two-level multifactorial designed experiments, the results of which allowed comparisons to be made between effects of individual and combined parameters on the laser inactivation efficiency. Escherichia coli was inactivated most effectively as a wet film with L. monocytogenes and S. aureus showing similar response. For the multifactorial experiments all laser parameters were significant and were smallest for S. aureus as a wet film. CONCLUSIONS: pH and NaCl concentration had little effect on the efficacy of laser inactivation but dry or wet states and all laser parameters were significant. SIGNIFICANCE AND IMPACT OF THE STUDY: Such systems may prove to be applicable in industrial processes where stainless steel may be contaminated with acidic solutions or salt, e.g. in the food industry with laser inactivation seeming to be independent of these parameters. Parameters have been identified that allow optimization of the treatment process.

Analysis of Variance↗