Fiberoptic Delivery System Research Articles

CONTACT NEODYMIUM

Contact Nd:YAG laser surgery offers a new method of delivering laser energy to a target tissue site. Nd:YAG, a near-infrared laser, can be transmitted through an optical fiber delivery system to a synthetic sapphire probe. This sapphire probe can be used as a surgical scalpel to cut, vaporize, or coagulate tissues. The contact laser scalpel offers many advantages over conventional steel scalpel surgery and the system overcomes many of the limitations encountered with noncontact Nd:YAG lasers. A review of the history, biophysics, and experimental studies is presented. Clinical oculoplastic applications are reviewed.

Requirements of an up to date fibre optics delivery system for laser medicine

The possibility of the potential as well as the safety of an optical fibre delivery system for laser medical applications is reviewed. Fibre directional couplers and connectors are suggested to be developed in view of this power laser application. Finally a special fibre probe radiating a corolla shaped beam for laser angioplasty is briefly described.

Erbium-YAG laser surgery on experimental vitreous membranes.

We used a pulsed erbium-YAG laser emitting in the midinfrared region (2.94 microns) to cut experimental vitreous membranes in rabbits via an intraocular fiberoptic delivery system. Thirty-four membranes were cut at distances of 500 to 3600 microns from the retina. All 34 of the membranes treated were effectively cut. Sixteen cases had no evidence of retinal injury, including one in which the membrane was only 800 microns from the retina. Retinal injuries in the remaining cases consisted of small (less than 300 microns) retinal burns and hemorrhages. In 94% of the cases with retinal injury, the fiberoptic was within 2000 microns of the retina. We conclude that a pulsed erbium-YAG laser allows near tractionless cutting of vitreous membranes and may have potential for clinical use if further studies show it to be efficacious and safe near the retina.

Welding of gallbladder tissue with a pulsed 2.15 microns thulium-holmium-chromium:YAG laser.

Percutaneous endoscopic approaches to cholelithiasis would be facilitated by methods for welding gallbladder tissues. We evaluated the bursting pressure and histologic appearance of canine gallbladder tissue welded with a thulium-holmium-chromium:YAG (THC:YAG) laser producing a 2.15 microns pulsed output. The tissue absorption characteristics at this wavelength as well as the pulsed nature of the output permit tissue welding with limited collateral thermal damage. The THC:YAG is compatible with a flexible fiberoptic delivery system. Bursting strengths of the welded junctions averaged 42 mm Hg, which is above physiologically encountered pressures. Histologic sections of the bonded tissues revealed tissue fusion and limited thermal injury to the surrounding tissue. We feel that THC:YAG laser welding may be a useful technique in the clinical development of percutaneous endoscopic biliary surgery.

High power optical fibre delivery system for the laser generation of ultrasound

A plastic-clad optical fibre system has been examined as a delivery system of pulsed laser energy for the generation of ultrasound. The onset of significant optical damage caused by the laser has been investigated. By using multimode fibres of ∼ 1 m length with 600 μm core size, it was found that laser power densities from the fibre were sufficient to produce ultrasonic waveforms corresponding to both the thermoelastic and plasma generation regimes. Out-of-plane acoustic displacements of >250 pm can be achieved through 2.5 cm thick aluminium test samples, showing that fibre optical delivery systems may be considered in systems using laser-generated ultrasound for non-destructive testing applications.

Laser angioplasty with a contact probe for the treatment of peripheral vascular disease.

Percutaneous transluminal laser angioplasty was carried out for the dilatation of 30 completely occluded peripheral arterial segments and three subtotal stenoses. A neodymium-YAG laser and an optical fibre delivery system with a sapphire tip were used. All three arterial stenoses and 26 of the 30 occluded arterial segments were successfully dilated. In 20 patients additional dilatation was carried out with a balloon catheter. Laser angioplasty failed to recanalise four occlusions, and vessel leakage without clinical consequences occurred in one patient. Reocclusion occurred within 48 h in two patients and after five months in one patient during a follow up period of at least six months. It is concluded that percutaneous transluminal laser angioplasty using direct contact with a sapphire tip is highly effective (89% success rate) in reopening peripheral vascular occlusions. The procedure is safe, and reocclusion of vessels is rare during the six month follow up period.

Experimental ab interno sclerotomies using a pulsed-dye laser.

We studied the use of a short-pulse, flashlamp-pumped dye laser, emitting at 666 nm, to create ab interno sclerotomies in cynomolgus monkeys using a fiberoptic delivery system. Because of the low optical absorption of the sclera in the visible portion of the spectrum, ablation of sclera by continuous wave lasers emitting in this region requires high energies and produces significant thermal damage to surrounding tissues. To enhance the optical absorption of sclera, methylene blue dye was applied iontophoretically; patent sclerotomies were obtained in all 10 eyes of six cynomolgus monkeys, with energies ranging from 15 to 50 mj/pulse. Thermal damage to the adjacent sclera was confined to 300 microns. Complications included mild intraoperative hyphema at all pulse energies and iridodialysis at higher pulse energies. Filtration blebs routinely failed within 7 days; the use of 5-fluorouracil postoperatively significantly prolonged bleb duration. The small incision technique described allows ab interno sclerotomies to be created with low pulse energies without the need for conjunctival dissection, thereby avoiding the problems associated with conjunctival wounds. An advantage of this technique is that it can be modified to create ab interno sclerotomies noninvasively by delivering pulsed visible radiation through the cornea with a gonioscopic-slitlamp system.

Preliminary evaluation of a pulsed 2.15-micron laser system for fiberoptic endoscopic surgery.

There is a need for lasers that are compatible with fiberoptic endoscopes and that provide greater cutting precision than currently can be produced by the widely used Nd:YAG (1.06 micron) laser. Recently available lasers that operate in the 2-micron region fill this need. This laser light energy can be transmitted by low OH- silica fibers and has much less tissue penetration than radiation at 1.06 micron. We have been evaluating a prototype solid state laser system that produces pulses of 2.15 microns light that is delivered by a silica based fiberoptic delivery system with negligible transmission losses. This system is based on a thulium-holmium-chromium doped YAG (Tm-Ho-Cr: YAG) rod that lases at 2.15 micron. The laser does not require cryogenic cooling, toxic gases, or custom utilities and should be practical in a clinical environment. In vivo animal testing of this laser confirms that it provides greater ablating precision than does the Nd:YAG laser at 1.06 micron.

The Nd:YAG laser 1.3 u wavelength: in vitro effects on ocular structures.

We evaluated the in vitro effects of the 1.3 u wavelength of a Nd:YAG laser using a fiberoptic delivery system, with or without sapphire tips on ocular tissue. Conjunctival and retinal adhesions were achieved best with a noncontact technique compared with a contact method.

Fiber Optic Pulsed Laser Delivery For Remote Measurements

The results of a research program on the delivery of high-peak-power laser light via fiber optics are presented. We discuss the influence of the host medium and the optical signals on the choice of fiber materials, complemented by a consideration of the measurement environment's effects on the quality of the data. We pay close attention to the choice of input/output beam/fiber coupling optics, nonlinear processes in the core, measurement system noise, and baseline drifts. Useful discussions of pulsed laser damage to optical fibers and data for optimization of a given fiber optic laser beam delivery system are given. As an example, details are given of the optical and instrumentational aspects of a particular fiber optic system developed for remote sensing of pressures and temperatures of UF6 gas in an operating advanced gas centrifuge.

Initial evaluation of the use of the potassium-titanyl-phosphate (KTP/532) laser in gynecologic laparoscopy

A new surgical laser, the potassium-titanyl-phosphate 532 nm laser (Laserscope, Santa Clara, CA) has recently become available for investigative procedures in gynecology. This article reports initial investigation of this laser energy at laparoscopy with the use of a flexible fiberoptic delivery system in rabbits and patients with endometriosis. Tissue effects on peritoneal structures of rabbits with laparoscopic firing of this new laser demonstrated the ability to accomplish surface vaporization without bowel perforation or penetration greater than 2 mm. In ten patients with pelvic endometriosis and pain, effective laparoscopic vaporization of implants has been safely accomplished with ease. Early follow-up revealed symptomatic improvement in all patients. This new laser is easy to use laparoscopically, appears safe in early investigations, and effectively reduces early postoperative pain associated with pelvic endometriosis.

Intravitreal argon and carbon dioxide laser, and xenon arc photocoagulation in vitreoretinal surgery.

Argon laser, carbon dioxide laser, and xenon arc endophotocoagulators have been used intravitreally to produce chorioretinal lesions during the course of the vitrectomy procedure. The advantages and disadvantages of each method of endophotocoagulation are presented. Both the argon laser and the xenon arc have a fiber optic delivery system. The carbon dioxide delivery system has a series of quartz waveguides transmitted through a miniature articulating arm. The advantages of using a carbon dioxide laser are its dual quality to act as both a photocoagulator and phototransector, its lack of pigment dependence, and its ability to deposit its energy in a well-defined area without adverse effects on neighboring ocular tissue.

Excimer laser angioplasty: Quantitative comparison in vitro of three ultraviolet wavelengths on tissue ablation and haemolysis

The effects of three ultraviolet excimer laser wavelengths on normal and atheromatous human cadaver aortic wall are presented. Ultraviolet radiation successfully ablates vessel wall; the dose response is greatest at 249 nm followed by 193 nm and 351 nm, where the effect is negligible for the equivalent energy dose. Wavelengths 249 and 193 nm have a selective effect on fibrous atheroma; ablation proceeds at a higher rate in this tissue. Non-linear effects observed at 249 nm may be due to thermal as well as photoablative mechanisms. In addition, blood samples were exposed to all three wavelengths and potassium concentrations were measured; the dose of energy required to produce tissue ablation may also produce significant haemolysis and hyperkalaemia at 249 and 193 nm but not with 351 nm. This finding may be important for coronary angioplasty but less so for peripheral work. The wavelength that produces the strongest dose response is 249 nm; this is the wavelength for which a fibre-optic delivery system should be developed.

Surgical Lasers and Soft Tissue Interactions

The different physical and biological qualities of the carbon dioxide, argon, and neodymium-YAG lasers provide the otolaryngologist and head and neck surgeon with a surgical tool with specific qualities and applications. The specific wave lengths of laser energy produce a varied soft tissue action. The carbon dioxide laser energy is absorbed by all biological tissues, whereas argon laser energy is an effective photocoagulator and penetrates into the subepithelial plane; the Nd-YAG laser creates a coagulation effect, which penetrates deep into the tissues. Each laser has specific physical qualities. The argon laser and the Nd-YAG laser can be transmitted through a flexible fiberoptic delivery system, whereas the carbon dioxide laser currently requires a rigid optical delivery system. The Nd-YAG and carbon dioxide lasers both require a second coincident aiming beam because of the invisibility of their laser energy, whereas the argon laser does not have such a requirement. The spot size of the laser beam can be much smaller for the argon laser than for the carbon dioxide laser. Protective lenses are necessary for the argon, carbon dioxide, and Nd-YAG lasers. The carbon dioxide laser energy is not transmitted through glass; thus most media (glass, plastic) are suitable to prevent any ocular injury. The argon laser requires a special yellowish protective mechanism, and the Nd-YAG laser requires a green protective lens mechanism. With further technical advances and improvements in the fiberoptic delivery system, smaller laser spot sizes, and changes in operating laser modes and color specifications of lasers, the advantages of laser surgery over conventional surgical techniques will become increasingly more apparent.

Variable section optical-fiber delivery system of high-power laser radiation for surgical use

Variable section optical-fiber delivery system of high-power laser radiation for surgical use

Laser Welding in Automatic Assembly Line for Color-CRT Electron Gun

YAG laser welding technology has been applied to an automatic assembly line for newly designed color-CRT electron gun. In the laser welding line, optical fiber delivery systems are used. This fiber is made from pure fused quartz. It has a 400 μm core diameter and a ten meter length. In using the optical fiber system, experiments are made to determine laser damage threshold in the fiber material versus high laser power density. transmission characteristics, life test and mechanical strength test. The develpment of this technique enables the laser optical system to be simplified, with higher flexibility, compared with coventional laser welding system using mirrors. In addition, simultaneous multi-spot laser welding and laser marking optical systems were developed. This welding line has markedly raised the productivity with higher product quality and reliability level.

Hepatic resection with an Nd:YAG laser in pig.

Eleven hepatic resections were performed by means of a divergent Nd:YAG laser. The beam was transmitted through a fiberoptic delivery system without any handpiece. The shortest resection time and most limited ischemic damage (4 mm) were obtained with 80-W power shoots and a low divergent beam (4 degrees 2 for full angle). The hemostatic effects of the Nd:YAG controlled bleeding from veins of up to 4.5 mm in diameter, and parenchymatic oozing from the cut edge minimized blood loss. Histological examination revealed the importance of cellular deterioration in the ischemic layer, while electron microscopy showed selective destruction of cell organelles and protein denaturation. Marked elevation of hepatic serum enzymes suggests a high degree of cellular damage. Postoperative examinations confirmed an uncomplicated healing process. Finally, the use of a flexible fiberoptic enables easy surgical manipulation.

The Application of GaAlAs Lasers to High-Resolution Liquid-Crystal Projection Displays

In this review we describe a high-resolution liquid-crystal (LC) display that uses multiple GaAlAs lasers to write on the LC cell. Arrays of high-powered lasers were needed to meet the writing speed requirements of the display. A fiber optic delivery system was developed to allow high-resolution, multi-spot writing on the cell, regardless of the laser configuration used. The fiexibility and unconstrained length of the fiber optics also permitted simplification in the design of the scanner system which moved the optical beams over the LC cell. Because of the proximity of the injection laser's wavelength to the visible spectrum used in the display projection system and because of divergence of the beams in the optical delivery system, a reflective LC cell was designed. Almost total absorption of the GaAlAs laser beam was achieved. This paper discusses the thermal and optical properties of the cell and their effect on the writing characteristics and the quality of the projected image (contrast and brightness). An off-axis projection system, which was designed for use with the reflective cell, creates a high-resolution image on the screen.

Laser scalpel for solid organ surgery

Hemostasis remains a major technical problem in surgery of the liver and spleen. A high power neodymiumdoped yttrium aluminum garnet (Nd:YAG) laser has been coupled with a fiberoptic delivery system and quartz blade designed to yield maximal hemostasis and minimal tissue injury. In a series of experiments we were unable to demonstrate a significant advantage of its use in partial hepatic lobectomy.

Gastric Hemostasis by Laser Phototherapy in Man

LASER energy has previously been shown to control bleeding from superficial gastric erosions in the dog. In the initial report by Goodale et al, 1 carbon dioxide laser energy was transmitted through a rigid, hollow endoscope. Subsequently, Nath et al 2 described a flexible fiberoptic delivery system through which argon laser energy could be transmitted. In 1975, Dwyer et al 3 reported the successful use of such a system to treat hemorrhage from superficial gastric erosions in dogs. This communication describes the use of argon ion laser phototherapy for the treatment of acute upper-gastrointestinal bleeding in man. Materials and Methods An argon ion retinal photocoagulator with a flexible fiberoptic delivery system was attached to the outside of an endoscope as previously reported. 3 The tip of the fiberoptic cable was covered by a protective cap, and the cap was equipped with two channels, one for water to wash the quartz