Progress report on extended clinical use of the argon laser for cutaneous lesions

Since 1970 a variety of cutaneous lesions have been successfully treated with the argon laser and the histopathology carefully studied at the Palo Alto Medical Clinic. Patients with port wine hemangiomas, capillary/cavernous hemangiomas, and telangiectasia have achieved successful resolution in some cases, and subtotal blanching in other cases, with a low incidence of scarring or other complications. Recently, decorative tattoos as well as a variety of miscellaneous pigmented or vascular skin lesions, such as seborrheic keratoses, pyogenic granulomas, and senile angiomas, have also been successfully treated with the argon laser. Total clinical experience is updated in this report.     

Gas volume quantitation during argon ion laser ablation of atheromatous aorta in blood and 0.9% saline media with an optically shielded catheter

Using an optically shielded fiber optic laser catheter, the amount of gas produced when firing an argon ion laser into 0.9% saline solution or blood alone and into atheromatous aorta in either a blood or 0.9% saline medium was quantitated. Energies from 0.25 to 4 joules (J) were used at powers of 2, 5, and 8 W. We found that total volume of gas produced is small not only at equilibrium (0.3 +/- 0.1 microliter/J when firing in blood alone and also when ablating aorta in blood or saline media) but also at peak (2.5 +/- 0.2 microliters/J firing in blood alone and 1.0 +/- 0.1 microliter/J or 0.9 +/- 0.1 microliter/J when ablating aorta in saline or blood, respectively). Because these volumes are small, a clinically significant event from a gas embolus is unlikely during intravascular laser ablation of atheromatous plaque in the energy and power range studied. No gas was quantitated when firing the argon ion laser into 0.9% saline solution alone. The peak gas volume when firing in blood alone was significantly greater than that produced in the other chamber environments. This is thought to be due to increased absorption of argon laser light by hemoglobin. The gas volumes produced by lasing aorta in 0.9% saline or blood were not statistically different.     

Reflectance during pulsed holmium laser irradiation of tissue

Although generally ignored in considerations of laser ablation of tissue, reflectance of laser light from tissue during laser-induced ablation is a potentially important factor in determining ablation efficiency because it determines the amount of laser light coupled into the target. To determine the significance of reflectance changes induced by laser irradiation, we examined the reflectance of liver samples during pulsed holmium laser ablation by placing the target at one focus of an ellipsoidal reflector and a detector at the other focus. The temporal behavior, total reflectance, and effect of multiple pulses were examined. Tissue reflectance as large as 50% was observed during holmium laser irradiation but depended upon laser radiant exposure and number of laser pulses. These measurements suggest that changes in the optical properties of the target during ablation are important and should be considered in detailed modeling of the ablation process.     

Tissue interactions and measurement of ablation rates with ultraviolet and visible lasers in canine and human arteries

Ablation rates measured as the depth of tissue excavation per unit time were determined in human and canine aortas subjected to radiation with ultraviolet (UV) excimer (ArF 193 nm, KrF 248 nm, XeF 351 nm) and visible lasers [continuous wave (cw) and 50-ms chopped argon ion, 478 nm-514 nm; pulsed double-frequency Nd:YAG, 532 nm]. For UV and pulsed double-frequency Nd:YAG lasers ablation rates were constant in time and depended linearly on average laser power, but for cw and chopped argon lasers ablation rates varied with irradiation time and were nonlinearly dependent on laser power. In human aortas, atherosclerosis without gross calcification had no influence on ablation rates. Charring and tissue disruption were observed with cw and chopped argon ion, whereas excimer and pulsed Nd:YAG lasers produced only minimal injury to surrounding tissue. We conclude that the determination of ablation rates is useful for the selection of laser wavelengths and power densities applicable to angioplasty and that UV and pulsed visible laser permit a better control of ablation compared to continuous wave lasers.     

Dependence of the XeCl laser cut rate of plaque on the degree of calcification, laser fluence, and optical pulse duration

A XeCl laser with an optical pulse duration of 35 ns was used to determine the cut depth per laser pulse of postmortem human aorta as a function of laser fluence for four main categories of plaque development. The data indicate that the cut depth per pulse progressively decreases as the degree of calcification increases even at very high (100 mJ/mm2) laser fluences. A comparison was made between the XeCl laser cut rate data obtained using the 35-ns duration laser pulses to data obtained using 200-ns duration pulses for each of the four plaque types. As the degree of tissue calcification increased higher XeCl laser fluences were required for the long pulse case to achieve the same cut depth per pulse as that observed using the shorter pulse duration.     

China report. II. Laser medicine in the People's Republic of China

The application of lasers to medicine in the People's Republic of China allready has an history of more than fifteen years. Lasers are being used in various clinical departments such as ophthalomology, dermatology, otorhinolaryngology, surgery, obstetrics, gynecology, neurology, psychiatry, internal medicine, and acupuncture. A brief account of basic research and instrumentation is also presented. The academic activities of laser medicine in China are increasing repidly, and sugestions for the establishment of a Chinese Laser Medical Society have been proposed. The prospectives for laser medicine appear brilliant and promising.     

Present status of laser neurosurgery

A three-fold approach to the status of laser neurosurgery was taken: 1) Questionnaire to Program Directors for neurosurgery training in the United States and Canada; 2) an analysis of titles in the preliminary neurosurgery program of the Fifth International Congress of Neurosurgery; 3) A literature survey covering the last 3 years of publication. The results showed increasing interest in the use of lasers in neurosurgery, especially for neoplasms in brain and spinal canal. The CO2 laser still dominates the field but Neodymium YAG is also finding wide use. The author comments on directions that laser neurosurgery may take in the future. Special emphasis is made on new applications combining advanced technologies, including CAT scanning, ultrasonography, stereotaxic techniques, and computer control.     

Investigation of carcinogenic effects of in Vitro Argon and CO2 laser exposure of fibroblasts

Mouse heteroploid fibroblasts were grown nine future generations in vitro tissue culture. The cells were exposed to argon laser, CO₂ laser, and x-ray. Results of scoring for mangnant transformation foci were tabulated and compared. Lasers did not produce a significant malignant transformation. Clinical laser use is reviewed and histology as well as long-term clinical experience confirms the safety of lasers.     

Laser applications to arteriosclerosis: Angioplasty,angioscopy, and open endarterectomy

We have studied laser radiation of arteriosclerotic cardiovascular disease to determine the best technique for evaluation. Rabbits with arteriosclerosis were treated by intraluminal laser angioplasty (N = 8), laser angioscopy (N = 2), and open laser endarterectomy (N = 5). All studies were performed with an argon ion laser delivering energy through a 400-μm quartz fiber. Power delivered was varied in order to determine the best value for this animal model. Following angioplasty, perforation was seen in three rabbits (in one case, it was due to mechanical trauma from the fiber optic), and early thrombosis occurred in two rabbits. Plaques were vaporized by angioscopy, but the depth of laser beam penetration or angle of incidence could not be controlled. Open laser endarterectomy gave consistently good results with removal of an arteriosclerotic plaque within the media. The optimum power was found to be 1.0-2.0 W. Endarterectomy required an energy density of 100-140 J/cm². We conclude that open laser endarterectomy can be a standardized technique for the in vivo evaluation of laser radiation upon arteriosclerotic lesions.     

Preliminary results of argon and carbon dioxide laser treatment of keloid scars

Argon and CO2 lasers have been used to treat 13 patients with well-established keloid scars of the trunk or earlobe. Multiple-bore-hole argon technique and total excision with the CO2 laser were attempted. One patient with an earlobe keloid responded to treatment, all other patients had no improvement.     

The influence of hands-on laser training on usage of the CO2 laser

A questionnaire was distributed to all participants in the Rochester General Hospital CO2 laser training workshops for surgeons (1982 to January 1985). The results of this study indicate that, while laser training is necessary prior to being able to use the laser, only a small fraction of trainees actually use the laser in their clinical practice. Surgeons who are using the laser do so in a minority of their cases. New incentives for laser usage must be investigated.     

Update on laser usage in treatment of decorative tattoos

This report updates our most recent series of 60 tattoos treated in 1980 and followed for at least 12 months. An initial rate of hypertrophic scarring of 35% at 3 months eventuated in 23% after 1 year. Factors such as sex, complexion, and body location were correlated to scars and hypopigmentation. Over 50% excellent to good results were achieved overall in this series.     

Extent of thermal penetration of Nd-YAG laser — histological considerations

Summary The extent of thermal penetration of Nd-YAG laser was studied histologically. The material was obtained from seven cases of various types of intracranial and extracranial tumours and normal temporal muscle obtained at operation. After irradiation of the tumour surface with the laser, the tumours were removed and depth and width of pathological changes caused by heat were studied. Histologically, materials consisted of a vaporized surface, carbonized, vesicular, necrotic, oedematous layers and surrounding intact brain tumour tissue. There was a direct relationship between the thermal effect and the irradiated thermal energy (watt × exposure time × pulse number). The results showed that the thermal effect was limited to a depth of 6 to 10 mm from the irradiated surface when irradiated 4 times at the power of 90 watts for 2 seconds.     

调Q1064nm激光和点阵1064nm激光治疗黄褐斑的临床研究

目的:探讨调Q1064nm激光和点阵1064nm激光治疗面部黄褐斑的临床疗效。方法:回顾性分析46例患者的临床资料,A组:24例,用调Q1064nm激光治疗,每月治疗1次,连续治疗5次;B组:22例,用点阵1064nm激光治疗,每2周治疗1次,每例患者治疗10次。两组患者均在疗程结束随访1年后进行评估。结果:A组24例患者经过调Q1064nm激光治疗5次后,临床治愈7例,显效12例,有效5例,无效0例,总有效率79.17%;B组22例患者采用点阵1064nm激光治疗10次后,临床治愈12例,显效7例,有效3例,无效0例,总有效率86.36%;两组总有效率比较无显著差异。结论:采用调Q1064nm激光和点阵1064nm激光治疗面部黄褐斑,有效、安全、无副作用,是目前治疗面部黄褐斑最有效的方法。     

Analysis of complications of argon laser treatment for port wine hemangiomas with reference to striped technique

Argon laser treatment of port wine hemangiomas has evolved greatly in technique. Since 1979, we have treated 150 patients with the "zebra strike" technique in order to enhance fading and lessen the incidence of complications or side effects. Eighty-one such patients are studied in depth with at least an 18-month follow-up on all patients. The "zebra stripe" technique is described in detail. Analysis of fading shows a 64% excellent or good result in all patients and analysis of sponginess shows that a marked reduction of sponginess is possible by the laser. Side effects and complications including hypopigmentation, texture change, and indentation are discussed in detail. Analysis of scarring shows an overall scar rate of 15% with a general scar rate of 7.4% if you exclude the lip and nasolabial area. Residual striping was present to a slight degree in 34% of the patients and to a major degree in 7% of the patients. All factors are discussed as far as age, complexion, sex, color or port wine stain and related to stripe technique.     

The importance of coherence length in laser phototherapy of gingival inflammation—a pilot study

The aim of this study was to investigate if coherence length is of importance in laser phototherapy. Twenty patients with moderate periodontitis were selected. After oral hygiene instructions, scaling and root planing (SRP), one side of the upper jaw was randomly selected for HeNe (632.8 nm, 3 mW) or InGaAlP (650 nm, 3 mW) laser irradiation. One week after SRP, the following parameters were measured: pocket depth, gingival index, plaque index, gingival crevicular fluid volume, matrix metalloproteinase (MMP-8), interleukin (IL-8) and subgingival microflora. The irradiation (180 s per point, energy 0.54 J) was then performed once a week for 6 weeks. At the follow up examination, all clinical parameters had improved significantly in both groups. A more pronounced decrease of clinical inflammation was observed after HeNe treatment. MMP-8 levels were considerably reduced on the HeNe side, while there was no difference for IL-8 or microflora. Coherence length appears to be an important factor in laser phototherapy.     

Controlling thermal damage of incisions using diamond, copper, and sapphire heat-conducting templates with and without cooling

INTRODUCTION: We investigated the reduction of thermal damage to the surrounding tissue when laser incisions were made with and without using thermal conducting templates at room temperature and cooled to 5 degrees C. STUDY DESIGN/MATERIALS AND METHODS: We used the Vanderbilt free-electron laser (FEL) at 5.4, 6.1, 6.45, and 7.7 microns. We also used a conventional continuous wave (CW) carbon dioxide laser at 10.6 microns. Incisions were made on 5x10 mm pieces of human breast skin (in vitro) and analyzed with histology. Computer morphometrics were used to measure the amount of thermal damage. RESULTS: All templates produced a statistically significant reduction in the thermal damage. Additionally, we showed that cooling the templates made a statistically significant greater reduction in the thermal damage. The cooled diamond template reduced the thermal damage from the FEL to 28% of the damage observed without a template. The same cooled template reduced the thermal damage from the CO(2) laser to 56% of the damage observed without a template. Lesser reductions were observed with the copper template and even less with the sapphire template. The sapphire template reduced the thermal damage to 39 and 67% of the damage observed without a template for the FEL and the CO(2) laser, respectively. CONCLUSION: These results indicate that unwanted lateral thermal damage from laser incisions can be reduced with cooled thermally conductive templates with the best results obtained with the diamond template, which is also the best thermal conductor.     

Clinical aspects of ophthalmic argon laser

This paper reviews the historical events leading to the development of the ophthalmic laser. The formation of the argon laser beam and its biological effects on ocular tissues are outlined, with the major emphasis on the retinal and choroidal tissues. The clinical indications, contraindications, and complications of ophthalmic argon laser photocoagulation for the anterior segment as well as the posterior segment structures of the eye are also thoroughly discussed.