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PubMed1998

Internally cooled power laser for MR-guided interstitial laser-induced thermotherapy of liver lesions: initial clinical results.

PURPOSE: To evaluate experimentally and clinically an internally cooled power laser system for percutaneous treatment of liver metastases, with magnetic resonance (MR) imaging guidance, to increase the volume of coagulative necrosis with single laser beam applications. MATERIALS AND METHODS: The power laser system consisted of standard cannulation paraphernalia and a specially designed 7-F protective catheter for cooling the laser tip during treatment to avoid carbonization. A microdome laser beam applicator with a laser tip diameter of 0.95 mm kept the entire device as small as possible. After the unit was tested in 40 porcine livers, 532 laser beam applications (mean power, 27.5 W [range, 22.1-30.0 W]; mean application time, 19.8 minutes [range, 14-30 minutes]) were performed with MR guidance in 127 patients with 318 liver metastases. The safety of the procedure and the volume of induced necrosis were evaluated. RESULTS: In vitro, cuboid areas of coagulative necrosis with a mean greatest diameter of 4.3 cm +/- 0.5 (SD) were demonstrated after single applications. In vivo, MR thermometry allowed accurate demarcation of changes induced by heat, with a mean diameter of necrosis of 3.3 cm +/- 1.4. No carbonization or vaporization of tissue or damage of equipment occurred during treatment. CONCLUSION: This power laser system can increase the volume of laser-induced necrosis in liver metastases with a single application, thereby simplifying and accelerating the treatment of larger lesions.

Animals↗

PubMed1993

Survival of patients undergoing Nd:YAG laser therapy compared with Nd:YAG laser therapy and brachytherapy for malignant airway disease.

Brachytherapy in combination with Nd:YAG laser therapy may add to the duration of survival of the palliative period when compared with laser alone. A retrospective study of patients with inoperable squamous cell carcinoma (SCC) was undertaken to determine if there was a difference in survival between those patients treated with Nd:YAG laser alone and those treated with Nd:YAG laser and brachytherapy. Twenty-two patients were treated with brachytherapy for malignant airway disease at our institution of which 13 had SCC. All patients had previously received treatment with Nd:YAG laser for exophytic disease. Survival was compared with those patients treated with Nd:YAG laser alone for SCC involving the airway. There was no statistical difference between the two groups with regard to age. The duration of survival of patients with SCC of the airway from the first Nd:YAG laser treatment was determined. A significant difference between those patients treated with Nd:YAG laser alone and those patients treated with combined therapy was found (p < 0.001). Brachytherapy may potentiate the duration of survival in patients with SCC involving the airway compared to palliation with Nd:YAG laser alone.

Aged↗

PubMed1994

In vitro studies on laser scaling of subgingival calculus with an erbium:YAG laser.

The effectiveness of a newly-developed Er:YAG laser with a fiber delivery system to remove subgingival calculus was examined in vitro. Fifty-three (53) periodontally-involved human extracted teeth with a band of subgingival calculus were used. Two experiments were conducted: in experiment 1, laser scaling was performed with water irrigation on a straight line and on a broad area, against the subgingival calculus at the energy levels of 10 to 120 mJ/pulse (3.5 to 42.4 J/cm2/pulse) and the pulse repetition rate of 10 pps. The morphological changes of the laser-scaled site were observed by SEM, and the efficiency of laser scaling was determined. In experiment 2, laser scaling was performed with and without water irrigation at 30 mJ/pulse and 10 pps. The morphological changes, the efficiencies, and temperature changes with and without water irrigation were compared. The pulsed Er:YAG laser used with water irrigation was able to remove the subgingival calculus from the tooth root effectively at the energy level of about 30 mJ/pulse (energy density: 10.6 J/cm2/pulse) and 10 pps, under in vitro conditions. Ablation of the tooth substance on laser scaling was generally observed within the cementum. There was little increase in temperature on the root surface during laser scaling. This study suggests the potential for the clinical application of the Er:YAG laser in subgingival scaling.

Analysis of Variance↗

PubMed1999

Experimental investigations on relationships between myocardial damage and laser type used in transmyocardial laser revascularization (TMLR).

Transmyocardial laser revascularization (TMLR) using a CO2 laser is clinically attempted in end-stage ischemic heart disease that is not treated by conventional bypass grafting or transluminal angioplasty. Besides, clinical trials of TMLR using a Ho:YAG laser have started recently. In this study, we compared the degree of damage to normal myocardium using these 2 types of lasers. Hearts of adult mongrel dogs were exposed under general anesthesia. Dogs were divided into 2 groups; those with channels made in the left ventricle by CO2 laser (CO2 group, n = 5) and those with channels made by Ho:YAG laser (Ho:YAG group, n = 5). The chest was temporarily closed, then serum MB isozyme of creatinine kinase (CK-MB) and troponin T (TnT) were measured sequentially. Twenty-four hours after laser irradiation, hearts were isolated for pathological studies with hematoxylin-eosin and Masson's trichrome stains. The CO2 group produced CK-MB with a peak of 1162.2 +/- 462.2 IU/l and the Ho:YAG group 1804.0 +/- 992.4 IU/l after 12 hours, and there was a significant difference between two groups (p < 0.01). The CO2 group produced TnT with a peak of 1.2 +/- 0.4 ng/ml and the Ho:YAG group 11.6 +/- 4.1 ng/ml after 6 hours, and the peak value in Ho:YAG group was significantly higher than that in the CO2 group (p < 0.001). Thirty channels were confirmed histologically in the CO2 group, and the width of thermal damage layer around the channel lumen was 249 +/- 83 microns. Twenty-seven channels were confirmed histologically in the Ho:YAG group, and the width of thermal damage layer was 760 +/- 288 microns. Thermal damage in the Ho:YAG group was significant greater than that in the CO2 group (p < 0.01). We concluded that TMLR using a CO2 laser is more suitable for end-stage myocardial ischemia than a Ho:YAG laser in terms of myocardial damage.

Aluminum↗

PubMed2000

Laser facial skin resurfacing: discussion on erbium:YAG and CO2 lasers.

There are two lasers for resurfacing. The erbium:YAG laser and the CO2 laser both have different physical and physiologic differences when striking the skin. Therefore, each laser gives a different result. This article reviews the use of the Sharplan Silktouch CO2 laser for 4 years and the erbium:YAG laser for 1 year. In the last year, we have performed 40 laser procedures with the erbium:YAG laser. Discussion ensues regarding the differences and similarities of the two lasers as well as the difficulties and complications.

Carbon Dioxide↗

PubMed2000

[Use of YAG-Selecta laser and argon laser in the treatment of open angle glaucoma].

INTRODUCTION: The falling success rate of ALT (Argon Laser Trabeculoplasty) has raised the interest in some new laser techniques, such as q-switched Nd:YAG laser trabeculoplasty (Coherent Selecta 7000). The "selective" laser trabeculoplasty destroys melanosomes of pigmented trabecular meshwork cells, sparing adjacent non-pigmented cells and tissues. AIM: Our goal was to establish the IOP lowering effect of selective laser trabeculoplasty (SLT--Selecta Laser Trabeculoplasty) in comparison with ALT. MATERIAL AND METHODS: We have examined 27 patients (10 men, 17 women) aged 35-82, with open angle glaucoma and visual field deterioration despite maximal tolerated topical therapy (21 patients--POAG, 3--NPG, 1--pigmentary glaucoma, 1--pseudoexfoliative glaucoma, 1--juvenile glaucoma). One eye of each patient was randomly chosen for SLT, the other eye underwent ALT. In each method 50 burns were applied in 180 degrees angle with power settings of 600-1000 mW for ALT and energy settings of 0.5-1.4 mJ for SLT. The IOP was measured 1 hour before laser treatment and 1, 2, 24 hours and 3 months after treatment. RESULTS: The mean initial IOP in eyes selected for SLT was significantly higher (21.26 +/- 4.82 mm Hg) than in eyes selected for ALT (20.26 +/- 4.01 mm Hg), t-test: p = 0.037. However, there was no statistically significant difference in the IOP lowering effect between eyes treated with SLT and eyes treated with ALT. The mean IOP drop from the pre-treatment values was -2.85 +/- 4.62 mm Hg after SLT and -2.63 +/- 3.60 mm Hg after ALT (t-test, p = 0.84). All values: 2, 24-hours and 3 months after treatment were significantly lower than pre-treatment values in both groups (t-test, p < 0.03). Only in the 1st hour after SLT the IOP drop was not significant. There was a significant correlation between the amount of pigment on the trabecular meshwork and the IOP fall (U Mann-Whitney test). In SLT group 6 patients (21%) developed mild iritis during 1st day after laser treatment, which disappeared after fluorometholon drop therapy. CONCLUSION: Both methods--SLT and ALT--have equivalent IOP lowering effect in short time observation (3 months). Due to entirely novel mode of Selecta laser action, long term results may show significant differences.

Adult↗

PubMed2002

[Lasers in dentistry. 5. The use of lasers in periodontology].

This literature review shows that the Nd:YAG laser and the Er:YAG laser can be beneficially used in periodontology for subgingival curettage and gingivectomy. Studies demonstrated that subgingival laser treatment can result in significant reduction of the initial levels of periodontal pathogens. It is beneficial to perform laser curettage under water irrigation prior to scaling in order to destroy of the structure of the calculus and its attachment to the root surface. During laser curettage sufficient haemostasis is obtained, which improves detection of subgingival calculus. Nd:YAG laser gingivectomy results in similar improvement of deep periodontal pocket as conventional flap surgery, with the advantages such as minimal bleeding and post-operative pain, no swelling, and neither sutures nor post-surgical dressing are needed. Both non-surgical and surgical laser treatments are often performed without local anaesthesia, making full-mouth treatment in one session possible. Treatments are well accepted by the patients and require about 50% less time than the conventional therapies. Laser-de-epithelialization for periodontal regeneration has been experimentally attempted, but more controlled studies are needed to establish its usefulness in the clinic. Laser treatment of peri-implantitis is not recommended.

Dental Calculus↗

PubMed1992

Do thermal lasers increase the risk of distal embolism in angioplasties? An experimental study with cw Nd: YAG and excimer lasers.

A thermal (contact cw Nd:YAG) and non-thermal (Xe-Cl excimer) laser were used to irradiate fresh human blood in an experimental setting to investigate the possible thrombogenic properties of lasers and to compare the two laser modalities. Blood was obtained into 10 ml citrate test tubes from healthy volunteers. Laser irradiations were performed with cw Nd: YAG laser (10W, 3 and 6 secs) and with excimer laser (20 mJ, 60 ns pulses, 15 secs). Altogether, 80 samples were collected. A thromboelastographic (TEG) analysis was performed for each sample as well as the controls, which were taken simultaneously. Serum potassium levels indicating haemolysis were also determined. Thermal laser energy seems to have more thrombogenic effect than excimer laser. There appear to be no previous reports available in the literature using TEG to determine thrombogenicity of different lasers.

Angioplasty, Laser↗

PubMed1988

[Percutaneous transluminal laser angioplasty in peripheral arterial occlusive disease--development of a new laser catheter system].

Percutaneous laser angioplasty in arterial occlusive disease has lately been performed clinically for the first time. Perforation of the arterial wall and formation of aneurysms are serious risks. Two novel laser catheters for laser angioplasty with minimized perforation risk are presented. Catheter I (5F) and II (6.3F) are designed in the same manner. The distal tip of these catheters is ovally formed and marked by a small X-ray dense metal ring. The silica fiber has a core diameter of 400 micron (I) respectively 600 micron (II). Its tip is also marked X-ray densely and therefore the position of the fiber tip can be controlled exactly during laser angioplasty. Using a guide wire and applicating short laser pulses the perforation risk can be minimized. In a total of 132 atherosclerotic stenosed or obstructed human arteries laser angioplasty was performed in vitro using a Nd:YAG laser. There were two perforations (1.5%). The degree of stenosis was reduced from 87 (90)% to 54 (52)%. Using the 600-micron-fiber (catheter II) the velocity of laser angioplasty was increased 2.5 times compared to laser angioplasty using the 400-micron-fiber.

Angioplasty, Balloon↗

PubMed1985

Factors contributing to perforations resulting from laser coronary angioplasty: observations in an intact human postmortem preparation of intraoperative laser coronary angioplasty.

This investigation was designed to assess the potential use of laser coronary angioplasty as an intraoperative adjunct in the surgical treatment of ischemic heart disease. Among 17 postmortem hearts, simulated laser coronary angioplasty was performed at 53 sites with a No. 4F guiding catheter and 240 micron (200 micron core) quartz optical fiber. Perforation complicated laser coronary angioplasty in 33 (62%) of the 53 attempts. Most (n = 29) perforations were thermal; four were purely mechanical. Perforation sites were characterized by extensive calcific deposits (21 of 33 cases [64%] ) and the origin of a side branch (13 of 33 [39%] ). Excessive tortuosity of the extramural coronary artery contributed to arterial perforation in four cases, and precluded attempts to perform laser coronary angioplasty in two other cases. In 19 of the 53 attempts to perform laser coronary angioplasty, a high-frequency two-dimensional echocardiographic probe was used to image the coronary artery during antegrade manipulation of the optical fiber/guiding catheter and laser irradiation of the target arterial stenosis. Although perforation nevertheless occurred in 11 (58%) of 19 sites, only one mechanical perforation resulted; the remaining 10 were thermal. Characteristics of the perforation sites in this group were similar to those noted for the group as a whole. Experience with this model of laser coronary angioplasty indicates that even when access problems associated with percutaneous laser coronary angioplasty are obviated by a simulated intraoperative approach, perforation of the underlying coronary arterial wall continues to represent the "rate-limiting" complication of laser coronary angioplasty. Most perforations occurred in relation to calcific deposits, branch points, and tortuous coronary segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1996

[Comparative study on diode laser (680 nm) and krypton laser mild photocoagulation--histological findings and therapeutic outcome for diabetic maculopathy].

A histopathological study of macaca monkey retina-choroid was carried out for one month after mild photocoagulation with a diode laser (680 nm) and a krypton laser (647 nm). Both lasers produced the same damage to the outer layer of retina and to the melanocytes of 1/3 of the inner choroid. Mild focal photocoagulation was done for 6 patients (12 eyes) with diabetic maculopathy. The patients were 41 to 67 years old, suffering from diabetes mellitus for 5 to 25 years. The grade of their retinopathy was Fukuda's classification AI, AII, and BI. AII eyes were tested before and 3-6 months after photocoagulation for corrected visual acuity, fluorescein angiography, and visual field sensitivity by Octopus automated static perimetry. Visual acuity was stable in all cases. Central sensitivity was better in 2 eyes and unchanged in 4 eyes in both types of laser photocoagulation. In cases of total loss, one eye was improved, 4 eyes were unchanged and one eye was worsened by diode laser photocoagulation and one eye was improved, 2 eyes were unchanged and 3 eyes were worsened by krypton laser photocoagulation. The diode laser (680 nm) might be as useful for ophthalmic laser treatment as the krypton laser.

Adult↗

PubMed2004