Tissue Vaporization Research Articles

Histological evaluation of the effect of a miniature carbon dioxide laser on oral mucosa

Carbon dioxide lasers emit infra-red radiation at a wavelength of 10600 nm, making them suitable for tissue vaporisation, incision and vessel coagulation. A miniature CO 2 laser (length 24 cm), with an output of 4 Watts focused on to a spot of 0.2 mm diameter at a distance of 2.5 mm from the nozzle tip, has been developed. This hand-held, water-cooled device operates off a 12 V D.C. source and provides good access to most areas of the mouth. In order to evaluate the use of the miniature laser, a series of lesions were produced on the lateral margins of sheep's tongues, and histological examination of tissues carried out immediately after treatment and at 1 h; 1, 2, 4, 7, 14, 21, and 28 day intervals. Wounds showed clean cut margins with even removal of epithelium and superficial connective tissue. Damage appeared to be restricted to a 100 μm deep zone in the lamina propria. Epithelial regeneration had commenced at between 2 and 4 days, and re-covered the surface by 14 days. A residue of chronic inflammatory cells was present within the stroma at 21 days, but this had resolved by 28 days. The miniature carbon dioxide laser is effective in vaporising oral mucosa and also achieving haemostasis by vessel coagulation; its manoeuvrability and relatively low cost warrant further clinical evaluation for the treatment of mucosal lesions, such as leukoplakia.

Transvascular Argon Laser Ablation of Atrioventricular Conduction in Dogs: Feasibility and Morphological Results

The purpose of this study was to ablate atrioventricular (AV) conduction in dogs with an argon laser using a transvascular approach. Six dogs were anesthetized and underwent a right thoracotomy and atriotomy. A bipolar #7 French lumen catheter containing a 400 u silica fiber was used to map the region of the AV junction. When a stable His deflection was obtained, the silica fiber was extruded from the end of the catheter and argon laser radiation was delivered for up to 20 s at 3.0-4.5 watts. In five of six dogs, complete heart block was successfully created after 3 to 15 lasings. A continuous His bundle electrogram in one dog showed gradual prolongation of the HV interval before the development of complete infrahisian block. The mean R-R intervals in the five dogs with complete heart block increased from 435 +/- 56 ms to 1216 +/- 197 ms (P less than 0.001), and the QRS duration increased from 78 +/- 26 ms to 91 +/- 19 ms (P = ns). Gross inspection showed multiple 1-2 mm2 craters in the atria just above the tricuspid valve ring. Complications included one instance each of aortic root perforation and creation of a small ventricular septal defect. These lesions were so small that there was no hemodynamic compromise in either animal in which they occurred and the lesions themselves were only detected on careful postmortem examination. Histology revealed two patterns of injury involved in conduction ablation. One was direct vaporization of tissue resulting in a wedge shaped incision and the other was formation of a hematoma and thermal necrosis at the lasing site with little evidence of tissue vaporization. Although catheter modifications are necessary to avoid perforation, this study demonstrates that ablation of conduction can be successfully accomplished using an argon laser.

Comments on 'Interaction of carbon dioxide laser radiation with ocular tissues' by T.J. Bridges et al

Previous experiments by Bridges et al. (in D.B. Karlin, 1984) on the interaction of carbon dioxide laser radiation with human eye lens tissue have been repeated. Contrary to previous results, it is found that there is a threshold fluence for the vaporization of lens tissue for its phototransection. Its average value is found to be about 26 J/cm/sup 2/ for 10.6- mu m radiation. Beyond this threshold fluence, the depth of incision increases with the interaction time of the laser beam. The possibility of thermal dissolution of cataractous eye lens tissue is explored and it is shown that with the CO/sub 2/ laser this is a high-temperature (270 degrees C) process, which makes it impractical for the removal of cataracts. >

Papillomavirus in the Vapor of Carbon Dioxide Laser-Treated Verrucae

Vapor produced by the carbon dioxide laser during the vaporization of papillomavirus-infected verrucae was analyzed for viral DNA content. Two models were used for evaluation: an in vitro cutaneous bovine fibropapilloma and an in vivo human verruca model. Four bovine fibropapillomas were exposed to various laser parameters with power densities of 38200 to 130 W/cm 2 and energy fluences of 3820 to 130 J/cm 2 . The generated vapor was collected in a chamber in line with a vacuum system. Hybridization with bovine papillomavirus DNA probes revealed intact bovine papillomavirus DNA for all power densities and energy fluences used. The laser vapor from seven patients undergoing carbon dioxide laser therapy for plantar or mosaic verrucae was also collected. Laser parameter settings were similar to those usually chosen for clinical tissue vaporization. Intact human papillomavirus DNA was present in the vapor from two of seven patients. These studies indicate that intact viral DNA is liberated into the air with the vapor of laser-treated verrucae. It would be prudent for all practitioners who use the laser in treating patients with viral infections or conditions associated with viruses to practice extreme care and safety throughout the laser procedure. ( JAMA 1988;259:1199-1202)

Laser treatment of rhinophyma.

The carbon dioxide laser, when used in the treatment of rhinophyma, allows accurate removal of the diseased tissue to the desired level without risk of exposure of any underlying osteocartilaginous structures. This ensures rapid reepithelialization that minimizes the untoward scarring that may occur from delayed healing using other sculpturing techniques. Precise tissue vaporization prohibits violation of surrounding normal tissues.

Fundamentals of laser light interaction with human tissue, especially in the cardiovascular system.

The absorption of single photons in the molecules of biological tissue can induce various reactions. For the most medical laser applications the transformation from radiation energy into heat is relevant. The laser beam is used for coagulation or vaporization of tissue. The changes in tissue, which are created by light of different wavelengths depends on the thermal and optical properties (absorption and scatting) of tissue but also on the parameters of irradiation. As an example measurements from human skin are discussed. In the cardiovascular system laser light must have a clearly defined effect. Atherosclerotic plaques of different consistence have to be vaporized without damage of the vessel walls. From different reasons the usual medical CW-lasers, Argon-laser, CO2-laser and Nd:YAG-laser, are not optimal for direct ablation of arterial occlusions. In order to mimize reocclusion the walls of the channels have to be completely smooth and free of coagulation necrosis. This can be obtained by short laser pulses. Selection of a light wavelength, which is stronger absorbed in atherosclerotic plaques than in vessel walls and additional selective staining are two ways to reduce the risk of damaging the vessel walls.

Papillomavirus in the vapor of carbon dioxide laser-treated verrucae

Vapor produced by the carbon dioxide laser during the vaporization of papillomavirus-infected verrucae was analyzed for viral DNA content. Two models were used for evaluation: an in vitro cutaneous bovine fibropapilloma and an in vivo human verruca model. Four bovine fibropapillomas were exposed to various laser parameters with power densities of 38200 to 130 W/cm²and energy fluences of 3820 to 130 J/cm². The generated vapor was collected in a chamber in line with a vacuum system. Hybridization with bovine papillomavirus DNA probes revealed intact bovine papillomavirus DNA for all power densities and energy fluences used. The laser vapor from seven patients undergoing carbon dioxide laser therapy for plantar or mosaic verrucae was also collected. Laser parameter settings were similar to those usually chosen for clinical tissue vaporization. Intact human papillomavirus DNA was present in the vapor from two of seven patients. These studies indicate that intact viral DNA is liberated into the air with the vapor of laser-treated verrucae. It would be prudent for all practitioners who use the laser in treating patients with viral infections or conditions associated with viruses to practice extreme care and safety throughout the laser procedure. (<i>JAMA</i>1988;259:1199-1202)

Papillomavirus in the Vapor of Carbon Dioxide Laser-Treated Verrucae

Vapor produced by the carbon dioxide laser during the vaporization of papillomavirus-infected verrucae was analyzed for viral DNA content. Two models were used for evaluation: an in vitro cutaneous bovine fibropapilloma and an in vivo human verruca model. Four bovine fibropapillomas were exposed to various laser parameters with power densities of 38,200 to 130 W/cm2 and energy fluences of 3820 to 130 J/cm2. The generated vapor was collected in a chamber in line with a vacuum system. Hybridization with bovine papillomavirus DNA probes revealed intact bovine papillomavirus DNA for all power densities and energy fluences used. The laser vapor from seven patients undergoing carbon dioxide laser therapy for plantar or mosaic verrucae was also collected. Laser parameter settings were similar to those usually chosen for clinical tissue vaporization. Intact human papillomavirus DNA was present in the vapor from two of seven patients. These studies indicate that intact viral DNA is liberated into the air with the vapor of laser-treated verrucae. It would be prudent for all practitioners who use the laser in treating patients with viral infections or conditions associated with viruses to practice extreme care and safety throughout the laser procedure.

Experimental retinochoroidal tissue vaporization with a CO2 laser probe.

The immediate and chronic effects of an intraocular carbon dioxide CO2 laser probe used for tissue vaporization were studied in cynomolgus monkeys' eyes. Acute lesions produced necrosis (from superficial to deep) of the retina and choroid, depending on the amount of energy used. Chronic lesions showed disorganization of the retina and choroid, with scar formation. Extensive tissue vaporization produced tractional retinal detachment in the chronic stage. Tractional detachment was prevented if the area of CO2 laser application was previously encircled with argon laser scars.

Electromagnetic field focusing system in the treatment of brain tumors.

The electromagnetic field focusing (EFF) probe, which is based on the principle of eddy current convergence, produces intense pinpoint heat at its point of contact with tissue. This allows cutting and vaporization of tissue and coagulation of vessels. The present experiments were conducted to study heat distribution to the surrounding tissue in brain and phantom and the effect on the brain of vaporization of intracerebral tumors in 19 rabbits. The follow-up period was as long as 47 days. The heating pattern showed a rise of temperature up to 250 degrees C at the probe tip, with minimal or no temperature increase at 2 mm and beyond. Minimal or no change was noted in the surrounding brain after tumor vaporization, indicating that this system would be safe in the vaporization of brain tumors in clinical neurosurgery.

Carbon Dioxide (CO2) Laser Therapy for Conjunctival Lymphangioma

Lymphangiomatous tissue involving the ocular adnexa may be difficult to manage because this highly vascular, unencapsulated tissue intermingles freely with normal adnexal structures. Hemostasis is difficult to obtain, and important ocular and periocular structures are damaged easily. We have successfully treated two individuals who had extensive conjunctival involvement of their lymphangioma with the carbon dioxide (CO2) laser. The CO2 laser permits a precise form of treatment with the ultimate form of hemostasis (tissue vaporization), resulting in minimal trauma, edema, and scarring, and thus offers a safe alternative to surgical excision of these lesions.

Ultrasonic and histopathological correlations of deep focal hepatic lesions induced by stereotaxic Nd-YAG laser applications

Thirty six deep focal hepatic lesions were induced in eleven piglets by means of an Nd-YAG laser. Laser shots of 80 W power and 10 s duration were used, the beam being transmitted through an echoguided stereotaxic handpiece. From day 0 to day 120, the animals underwent ultrasonographic and morphological controls. At lasering time an hyperechoic image—12–18 mm in diameter—appeared due to boiling of tissue water. During the twenty postoperative days the lesion core was an echo-free area due to tissue vaporization, surrounded by an hyperechoic ring of increasing fibrosis, containing neovascularization and biliary ductules, while the hypoechoic outer area represented the peripheral halo of edema. In the long term, hyperechoic structures—swollen fibrotic septa of homogeneous fibrotic network—invaded the lesion site confirming good healing.

Carbon Dioxide (CO2) Laser Therapy For Conjunctival Lymphangioma

Lymphangiomatous tissue involving the ocular adnexa may be difficult to manage because this highly vascular, unencapsulated tissue intermingles freely with normal adnexal structures. Hemostasis is difficult to obtain, and important ocular and periocular structures are damaged easily. We have successfully treated two individuals who had extensive conjunctival involvement of their lymphangioma with the carbon dioxide (CO2) laser. The CO2 laser permits a precise form of treatment with the ultimate form of hemostasis (tissue vaporization), resulting in minimal trauma, edema, and scarring, and thus offers a safe alternative to surgical excision of these lesions.

Nd-YAG laser-induced injury in dog myocardium: optical and ultrastructural study of early lesions.

To characterize myocardial lesions induced by Nd-YAG laser in vivo, laser pulses were delivered on the epicardial surface of beating dog hearts. Acute lesions were studied at the optical and ultrastructural levels. The size of the lesions depended on the power of the laser beam. Tissue vaporization could be avoided if total delivered energy did not exceed 350 J. Laser energy induced different types of myocardial necrosis distributed in concentric layers of coagulation necrosis, and contraction band necrosis. Thus, laser energy can produce controlled irreversible lesions without crater formation. These effects may be of use in the treatment of arrhythmias.

Carbon dioxide laser treatment of cervical stenosis

Fifteen women diagnosed with cervical stenosis were treated by vaporization of scar tissue using the carbon dioxide laser. Ninety-three percent of the cases demonstrated binding constriction of the cervical os to a 2-mm diameter or less and 40% of the cases had either a pinpoint opening or total endocervical obliteration. The technique for laser treatment and the success of the method depend on precise variations of mode, power, beam diameter, and "buttoning" the endocervical mucosal remnant. Twelve of the 15 patients were relieved of stenosis and 9 achieved pregnancy within 2 years of the operative procedure. Critical analysis of possible causative factors in this study revealed that virtually every case of stenosis had been iatrogenic.

The effects of laser smoke on the lungs of rats

The sequelae of long-term inhalation of carbon dioxide laser smoke on 10 white rats were studied in a three-phase experiment. The fine particulate matter resulting from tissue vaporization was deposited in the animals' alveoli, which produced congestive interstitial pneumonia, bronchiolitis, and emphysema. The pathologic findings induced by laser plume are not dissimilar to those resulting from the long-term inhalation of other types of particulate matter. Use of an efficient smoke evacuator should offer substantial protection against these normal effects.

Comparative Efficacy of Continuous and Pulsed Argon Laser Ablation of Human Diseased Ventricle

We compared the tissue lesions obtained in a saline medium using single continuous argon laser discharges with paired sequential continuous laser discharges in nine segments of diseased human ventricle resected from patients with and without ventricular tachycardia (VT) at cardiac surgery. Single continuous argon laser discharges were delivered to separate sites on the endocardial surface of the tissue segments for periods of 10, 20, and 30 seconds at laser beam power of 5 W (group IA) and 8 W (group IIA). Paired sequential argon laser discharges of 5, 10, and 15 seconds in duration were delivered to separate sites at a laser power of 5 W (group IB) and 8 W (group IIB). Gross and microscopic examination of each tissue lesion and its dimensions were performed. Laser irradiation of excised human ventricle resulted in a circular discrete burn at the site of application. Histologic examination showed crater formation due to tissue vaporization with the crater lining consisting of charred tissue and a zone of coagulation necrosis. Analysis of lesion dimensions in groups IA and IIA showed comparable lesion depth and diameter with single continuous and paired sequential laser discharges at energies of 50 J (p greater than .2), 100 J (p greater than .2), and 150 J (p greater than .2). Similarly, lesion depth and diameter were comparable in groups IB and IIB at the same energies. We conclude that paired sequential argon laser discharges may be used to produce comparable tissue lesions to single continuous argon laser discharges in diseased human ventricle.

Endobronchial Management of Lung Cancer

Bronchoscopic phototherapy is available now for 2 distinct categories of tracheobronchial cancer: roentgenographically occult superficial squamous cell carcinoma and advanced malignancy causing significant airway obstruction. Laboratory and clinical experience show that the photodynamic effect of hematoporphyrin derivative phototherapy (HpD-PT) may be useful for treating superficial cancers that penetrate less than 5 mm into bronchial mucosa. The larger, obstructing cancers are better managed by high-power laser sources, such as the YAG laser, which are effective by hyperthermal photocoagulation, thermal necrosis, and tissue vaporization.

Urologic dosimetry studies with the Nd: YAG and CO2 lasers: Bladder and kidney

Dose recommendations for the use of the Nd:YAG and CO2 lasers have been accepted with little laboratory analysis. We have examined both endoscopic and open applications in the bladder and open applications on the kidney with the lasers over a variety of power and pulse duration settings. In addition, we have studied the effect of varying the temperature of the tissue and irrigation solution on the depth of penetration. We found that with the Nd:YAG laser, the maximum depth of penetration in our animal model was only 2.62 mm in the bladder. This occurred during an endoscopic treatment with settings of 50 W at 4 seconds with irrigation solution of 25 degrees C. The depth of penetration using current recommendations of 40 W for 2 seconds was less than 1 mm at all temperatures. Room temperature irrigation solution may be the ideal compromise, but higher-power long-pulse durations or repeated treatments to the same area may be necessary to achieve penetrations of 3-5 mm. In open applications on bladder and kidney, the maximum depth of penetration in our animal model was 2.75 mm, which was found during a treatment with settings of 60 W at 4 seconds with the kidney parenchyma at 25 degrees C. Using the CO2 laser on open applications of bladder strips, we obtained a maximum depth of penetration of 1.75 mm at 30 W of power for 1/2 second at 85 degrees C tissue temperature. Unfortunately, penetration by the CO2 laser is accompanied by vaporization of tissue, leaving a large crater. Minimal injury exists beyond this area. In the kidney, we obtained a maximum depth of penetration of 1.75 mm at 30 W of power at 25 degrees C and 20 W of power at 2 degrees C each for 1/2 second.

Acute continuous argon-laser induced tissue effects in the isolated canine heart

Fresh isolated myocardial, elastic-arterial, and valvular tissues from seven canine hearts were irradiated by argon laser. Irradiation was transmitted through 300 and 400 μm flexible quartz fiberoptic elements. Minimal power densities for vaporization of the myocardial, arterial, and valvular tissues were 80, 90, and 110 W/cm 2, respectively, with maximal vaporization distances (fiberoptic tip to tissue) of 4 mm, 1 mm, and 1 mm, respectively. Irradiation of the valves at power densities approaching perforation caused contraction of the tissue. When tissue vaporization occurred, histologic examination of irradiated tissues showed a central crater surrounded by sequential layers of char, vaporization, and coagulation necrosis. These findings were common to all cardiac tissues. Additional findings unique to myocardium were a normal-appearing myocardial layer (skip-area), circumferential halo, and tissue clefts. Elastic arteries showed concentration of necrosis around the collagen and elastic fibers. Valvular damage was the most extensive and also included contraction of adjacent valvular tissue and endocardial sloughing.