The milliwatt CO2 laser and a thermal activated binding compound (20% serum albumin) were used for microvascular anastomoses. Under general anesthesia, the femoral arteries (0.7 to 1.0 mm diameter) of 6 rats were isolated. After the left femoral artery in each rat was clamped and transected, the vessel was held together with 3 equidistant 10-0 Xomed sutures. The cut edges were coated 3 to 4 times with the albumin solution and sealed with the CO2 laser (power density = 120 W/cm2). The binding compound solidified to a translucent tensile substance which supported the anastomosis until self healing and repair were achieved. The right femoral artery was used as sham operated control. Complete hemostasis and patency were observed in every case immediately and at 1, 3, and 6 months following surgery. The binding compound absorbed most of the laser energy thus minimizing thermal injury to the underlying tissue. Mongrel dogs weighing 28 to 33 kg were anesthetized and prepared for sterile surgical procedures. In 5 dogs, the femoral and jugular veins were exposed, transected, and anastomosed using a CO2 laser (Sharplan 1040) with the binding compound. In another 12 dogs, cephalic veins were isolated and used for aortocoronary artery bypass procedures. The Sharplan 1040 CO2 laser and 20% albumin solution were utilized to complete the coronary anastomoses in 6 dogs, and 6 dogs were used as controls by suturing the vessels. Again, hemostasis, patency, and minimal tissue damage were observed immediately and 6 weeks after the procedures. Improved surgical results, reduced operating time, minimized tissue damage, and enhanced anastomotic integrity are the advantages of laser assisted vascular anastomosis with a thermal activated binding compound.

This article reviews recent data on milliwatt CO2 laser-assisted arterial anastomoses as an update to the review presented at last year's SPIE conference. Highlighted are the basic mechanical properties of vascular repair. New information which strengthens or refutes past theory about laser repair is also considered.

The technique for CO2 laser fusion vascular anastomosis in normal vessels has been well established. Normal arterial wall has a predictable thermal response to the incident laser energy, with rapid heating and cooling of collagen within the arterial wall. Since atherosclerosis involves subendothelial cellular proliferation, lipid and calcium deposition, it may modify the thermal responsiveness of the arterial wall. To this study, CO2 laser fusion anastomoses were attempted in rabbits with non-calcific atherosclerosis and humans with calcific atherosclerosis. All anastomoses were successfully completed without alteration in technique despite the presence of plaque at the site of laser fusion. Histology of rabbit vessels revealed the classic laser fusion cap within the adventitia and persistent atherosclerotic plaque at the flow surface. Duplex imaging of patients post-operatively demonstrated long term anastomotic patency in 2 of 3 fistulae. These results suggest that neither non-calcified or calcified atherosclerosis significantly alters the arterial wall thermal responsiveness to CO2 laser energy or inhibits creation of laser fusion anastomoses. Therefore, this technique may be applicable to the treatment of patients with atherosclerotic occlusive disease.

Tissue fusion by laser energy is an intriguing arxi very promising new application for laser technology. In coniparison to using high laser energy to ablate tissue as in the aricplasty application, laser tissue fusion is possible in any soft tissue by deliverir appropriate lc levels of energy to the cppose tissue surfaces. This technology is particularly appealing for vascular applications in inakir sutureless blood vessel anastornosis and for securir the endpOints of erxarterect:amies ani dissection planes. Although there have been limitel evaluations of this technology the preliminary experimental ar1 clinical data is very promisir for continu development arid application.

Sutureless end-to-end ileo-ileal intestinal anastomoses were successfully constructed with both the 1.06 jim neodymium:YAG and the 488/515-nm argon lasers. A 5-watt power setting was used with the neodymium:YAG, and various biologic solutions were added to the anastomotic seam during lasing. Power settings of 1.5, 3, 4, and 5 watts were used for argon lasing, with and without an exogenous chromophore. At the 4-watt argon setting, a continuous infusion of normal saline was dripped onto the anastomosis during lasing, replacing the chromophore. All bowel anastomoses were constructed with the aid of a biodegradable intraluminal stent that held the bowel ends in place during construction of the watertight ileal fusion and then completely degraded within 8 hours. We concluded that the neodymium:YAG seemed superior for tissue fusion using the techniques outlined, as it was associated with fewer anastomotic leaks. It appeared easier to determine the end-point of tissue fusion with the neodymium:YAG than the argon, because the tissue changes were more obvious during neodymium:YAG lasing. The deeper penetration into the bowel wall of neodymium:YAG laser energy may confer a welding advantage over the more shallow penetration of the argon wavelength.

In an attempt to overcome some of the problems associated with conventional wound closure, i.e. suture or mechanical device closure, the laser has been used for "tissue welding" (sealing or fusion), of wound edges. Early attempts at laser sealing were centered on microvascular anastomosis and recent studies have been extended to include most soft tissues. It has been demonstrated in animal studies that the process of healing after laser wound closure is very similar in most tissues. Within the past year alone the experimental work in this area has progressed rapidly and limited clinical trials are now under way. Based on our results in detailed animal studies and in limited clinical experience, laser tissue sealing has the potential to augment or replace many conventional techniques of wound repair.

Laser-assisted microvascular anastomoses and nerve anastoriioses can be performed with the most diverse types of laser (1-17). However, postoperative complications in the form of thromboses and aneurysmal sacs as well as neuromas could be detected in longitudinal investigations. By conversion of the beam geometry (1.32-pm Nd: YAG laser, 200-pm, light conductor) and use of two or three concentrically applied 10,0 stay sutures, early and late complications could be markedly reduced. Histological and fine structural analysis revealed a homogenizing change of collagen with interdigitation of altered individual fibrils that appeared to be the structural equivalent of the welding effect (12).

Percutaneous endoscopic techniques for biliary surgery would be facilitated by methods of welding biliary tissue. To further investigate laser methods for fusing biliary tissue, we compared the time 0 bursting strength of two variations of near-infrared laser closure against polyglycolic acid suture controls. These time 0 studies were performed with a gallium-aluminum-arsenide semiconductor diode laser with a major ,iavelength output of 808 -F 1 nm and an energy density of 4.8 J/cm'. Using the 808 nm laser and indocyanine green dye to enhance laser energy uptake, closure of gallbladder incisions was accomplished with and without addition of fibrinogen to the target site prior to laser exposure. Without fibrinogen, the laser welds burst at 77 mm Hg, while fibrinogen soldering yielded a bursting pressure of 194 mm Hg. Sutured welds leaked at 215 mm Hg. Survival studies were performed with a mid-infrared 2.15 micron thulium-holmium--chromium:YAG laser producing 200 microsecond 300 millijoule pulses at 3 Hz (peak power .75 megawatts/sq cm, fluence 150 joules per square centimeter). The healing of midinfrared and polyglycolic suture closures of gallbladder incisions were compared at 1,2,3, and 4 weeks. All closures healed without evidence of leakage or infection. Laser welded cholecystostomy sites were completely ingrown with fibrous tissue by 2 weeks post- operatively and re-epithelialized by 3 weeks after operation. Suture closed wounds were still without complete epithelization 4 weeks after the procedure. Laser welding, particularly with fibrinogen reinforcement, may be a useful technique in future developments in percutaneous endoscopic biliary surgery.

A major obstacle to lung transplantation and combined heart- lung transplantation is dehiscence of the tracheobronchial anastomosis. We explored the possibility of laser welded anastomoses in canine tracheas in vivo. Laser anastomoses were performed on three-quarter circumferential anterior tracheotomies. A continous wave diode laser (808 +1 nm) at a power density of 9.6 watts/cm was used. Human fibrinogen was mixed with indocyanine green dye (ICG, max absorbance 805 nm) and applied to the anastomosis site prior to laser exposure. Animals were sacrificed at 0, 21 and 28 days post-operatively. At sacrifice weld bursting pressures were measured by raising intratracheal pressure using forced ventilation via an endotracheal tube. Sutured and laser welded anastomoses had similar bursting pressures, and exhibited satisfactory histologic evidence of healing. However, compared to polypropylene sutured controls, the laser welded anastomoses exhibited less peritracheal inflammatory reaction and showed visibly smoother luminal surfaces at 21 and 28 days post- operatively. Tracheal anastomosis using ICG dye enhanced fibrinogen combined with the near-infrared diode laser is a promising extension of the technology of laser tissue fusion and deserves further study.

Concerning hyperthermia treatment, knowledge of time-temperature and of temperature distributions within tumor volumes is essential to obtain a maximal therapeutic effectivity. New techniques are developed to overcome these difficulties. Two different heat sources, the contact Nd:YAG laser system and the automatically controlled highfrequency current are investigated. In a defined volume of 1 cm3, the laser system reaches 45°C after 1.8 s exposition with 15 W output power. The highfrequency current reaches 45°C after 48 s exposition with 18.75 W output current. Both heat sources present an exponential decrease of the temperature profile depending on the distance and prove efficient for inducing anti-tumoral hyperthermia. The tissue heat clearence is compensated for by intermittent laser and highfrequency current application.

We have conducted a study of the use of the carbon dioxide (C02) laser for ablation of multiple cutaneous recurrences of melanoma. Lesions of primary malignant melanoma are usually widely excised to try and prevent local recurrence. Despite this, recurrent cutaneous lesions do occur. These lesions may be small and numerous making local excision impractical. Hyperthermic isolated limb perfusion has shown some success in controlling the local disease but this procedure has a significant morbidty, some patients show only a limited response and post-perfusion recurrences are common.1 Also, in some patients, thelesions will not be confined to a limb. No other method of local control has provided an ideal solution and amputation has sometimes been a last resort. We have therefore selected patients for laser ablation if they have had lesions too numerous for local excision, or have had recurrences following perfusion or were otherwise suitable for perfusion. The lesions were vaporized under local or general anaesthesia according to their size and number. The wounds were then left to heal by secondary intention. Simple dry dressings were applied and all patients were discharged home within 24 hours. In total we have treated over 1,500 lesions in 30 patients. The results of the initial study have been very encouraging. The procedure is quick and simple with absent or minimal post-operative pain. Although the incidence of recurrent tumour at a previously lasered site is less than 1%, new tumours may develop at other sites. These are amenable to further laser treatment.

Recent clinical research on the use of ruby lasers for the treatment of tattoos and FIlk approval of a commercial system have renewed interest in this device. In this paper the principles of Q-switched ruby laser operation are reviewed, and potential sources of error in the estimation of delivered fluence are discussed.

The puleed dye laser habesn used clinically at DUE institution thce October 198. InItiall.y It was used via conventional urtttroscopes of 11.5 F. With the development of a purpose-buit, miniaturised ureteroacope (7.2!) laser fragtnentation has become more effective and complications have been roduoed, Active1y-def1ectible ureteroecopes (9.5!) enable access to calculi in aintost a]]. clinical situatiotie. The impact of tha laser has baan fragmentation vhich is safer than electrohydrai1ic probea arid with less heat production than ultrasonic probos. More important still has been its Impact on ureteroecopy foi acees.

For laser lithotripsy with s pulses there have only been dye lasers available with fixed pulse length and pulse shape. The development of a pulse stretched Alexandrite laser offers the possibility to control these parameters, thus to find their optimum for lithotripsy. This paper describes the laser system and reports on the first results that have been achieved concerning fiber transmission with extended pulses, fiber damage thresholds, fragmentation rates avoid adverse tissue effects.

We report the use of a 308 mu XeC1 exciiuer laser for- biliary stone fragnientation. The 130 nsec laser pulses are delivered through tJV grade fused silica fibers to the target stones inmiersed in normal saline solution and placed in direct contact with the fiber. Sixty biliary calculi, 20 cholesterol and 40 pigment, were fragmented in vitro. The effect of laser repetition rate, energy fluence, and fiber core size on stone fragmentation was studied. Fragmentation thresholds for biliary calculi of different compositions were measured. It was found that higher fragmentation efficiency was obtained with larger fluence, lower repetition rate and fiber of larger core. Our study suggests that the long pulse 308 nm excimer laser may be an effective device for laser lithotripsy with low threshold and good efficiency for biliary stone fragmentation.

For the laser-induced shockwave lithotripsy the electromagnetic energy of a laser light pulse is converted intracorporally into the acoustic energy of a shock wave. The lithotriptor is based on a specially developed, Q-switched Nd:YAG laser whose high power light pulses (70 mJ, 25 ns) are coupled into a flexible quartz fiber of 600 pim core diameter. Using focussing elements energy densities higher than 6 1O J m2 can be achieved resulting in an optical breakdown in water followed by a shock wave. As a result of different absorption mechanisms the breakdown threshold can be decreased by placing a metallic target into the laser beam. The different shockwave formations of such optomechanical transducers have been measured. First clinical applications have been performed.

Fiber tip breakage during urinary and biliary laser lithotripsy has been recognized to occur with several laser types. This phenomenon has also been seen with Q-switched Nd:YAG laser lithotripsy. Our aim was to determine the biological consequences of this event in the canine ureter and bile duct. In an excised tissue preparation, urinary and biliary stones were impacted in a canine ureter and common bile duct. Three and four hundred micron quartz laser fibers were placed in direct contact with the stone. Normal saline coaxial irrigation was initiated at 75 xal/min. A Q-switched Nd:YAG laser was activated at repetition rates from 1O-30 Hz. and pulse energies from 10-30 mJ. The tissue was sectioned and microscopic examination of the fragmentation site was performed. Histological exam revealed the persistence of large numbers of fiber fragments in the lumen and imnbedded in the epithelium at the lithotripsy site. Fragments varied greatly in size and appeared to have angular, sharp edges We conclude that irrigation can not be relied upon to remove the fiber fragments from the lithotripsy sites and that the biological consequences of fiber fragmentation may be greater than previously believed. Glass fragments "blown" into the epitheliumu will often result in glass granulomas, which may eventually cause obstruction of closed lumninal structures. This raises serious concern for the presence of any fiber breakage during laser lithotripsy.

At present the laser induced shock wave lithotripsy (LISL) of urinary and biliary stones via fiber optic beam delivery is governed by two competing' laser systems: The flashlamp-pumped pulsed dye laser and the Q-switched Nd:YAG laser. The pulsed radiation of the dye system with pulse durations in the 1-2 .tsec region can be easily transmitted through extremely flexible fused silica fibers with core diameters of only 200 im whilst the Q-switched Nd:YAG laser with pulselengths of 5-25 nsec needs fibers with more than 400 tm core diameter. The dye laser releases acoustic shock waves for fragmentation simply by stone contact, the Q-switched Nd:YAG produces these waves in the surrounding aqueous medium by laser induced optical breakdown (LIB) when refocused by optical means or through additional metal absorbers, i.e. opto - mechanical couplers. We report on the system performances and laser/stone interactions of two alternative solid-state laser systems with variable pulselengths in the range of 1.7 - 30 sec and 30 - 1000 nsec, respectively: The pulsed psec-Nd:YAG laser and the Q-switched alexandrite laser. Regarding the endoscopic laser lithotripsy of urinary and biliary stones in the ureter or common bile duct, respectively, the laser energy delivery system, i.e. the optical fiber; is the most stressed part. Therefore we used long-pulse solid-state laser systems like the pulsed Nd:YAG laser with a pulse-slicing unit and a pulselength-tunable Q-switched alexandrite laser and studied fragmentation of synthetic plaster samples as well as urinary and biliary stones. The radiation of both laser systems can be effectively transmitted via standard 200 im core diameter optical quartz fibers what is absolutely necessary when used in conjunction with small caliber rigid or flexible endoscopes. As a compact and reliable solid-state system the alexandrite laser lithotripter is much less expensive than an extracorporeal shock wave lithotripter with the same fragmentation results and may become the laser of choice for LISL.

In vitro study: 53 calculi were fragmented (Technomed pulsolith, 6OmJ/pulse, 2Hz). Initial visible stone damage and disruption into at least 2 large pieces were rapidly achieved (means of 20 to 1 53 pulses respectively). The disintegration to fragments 5mm or less was obtained after a mean of 780 pulses and required for 26% of stones more than 10 mm to be achieved. Decreasing stone size, stone mass, and an increasing bilirubin with a decreasing cholesterol content correlated significantly with the more rapid achievement of satisfactory fragmentation.

Laser lithotrpsy has shown an increasng potential during the last few years to have a rational n the treatment of ureteral calcufl. !n-vtro measurements of the fragmentation rates of the Nd:YAG laser, pulsed dye laser and alexandrfte laser have been performed using natural human calculi. Both, the dye and the alexandrite laser gave reasonably effective fragmentation rates against most types of calculi tested. The effect of different fiber diameters and different energy levels on the fragmentation rates were studied, in order to define the optimal working parameters for each system. Limited energy range and the requirement of an optomechanical coupler were the main disadvantages of the Nd:YAG laser. The dye laser showed optimum effects using a 200 um fiber at 5O..60 mJ pulse energy. At higher energy levels, the system worked better and produced more effective fragmentation using a 300 um fiber. At comparable energy levels, fragmentation effects were higher for alexandrite and dye laser systems compared to the Nd:YAG laser system.

Two different systems for laserlithotripsy - the Q-switched Nd:YAG laser with an optomechanical coupler and the flashlamp pumped dye laser with integrated optical feedback mechanism are in clinical use for the treatment of urinary calculi at the Department of Urology of the Medical University of LUbeck. Seventy-five patients with ureteral calculi have been treated by laser lithotripsy. Eleven of 15 treatments using the Nd:YAG laser have been performed under visual control with the help of a rigid ureteroscope of 11.5 F. Thirty-five of 42 treatments with the dye laser were carried out with the help of a rigid ureteroscope of 9.5 F. Four patients with the Nd:YAG laser and 7 patients with the dye laser, respectively, have been treated without visual control using a flexible application system and fluoroscopy alone. Both systems showed excellent results. Fourteen of 15 laser lithotripsies with the Nd:YAG laser were successful showing complete (4 cases) or partial (10 cases) fragmentation. The analysis of the failure showed calcium oxalate monohydrate. Thirty-eight of 42 laser 1 ithotripsies with the dye laser were successful. Fragmentation was complete in 26 and partial in 12 cases. The 4 calculi which proved to be failures were all of pale color and 2 of them consisted of cystine alone. Both laser systems are suitable for the treatment of ureteral calculi under visual control or by blind application using fluoroscopy. No serious side effects of the treatment have been observed. Treatment results are satisfactory. Problems may occur in calculi of hard structure using the Nd:YAG laser due to its limited energy and in pale-colored stones using the dye laser due to poor absorption of the laser energy.

This study describes the use of a microcomputer based assessment and control system, devised by the authors, for the treatment of Port Wine Stains. In the theoretical model under development, the haemangioma was represented as a discrete blood layer within the dermis, the haemoglobin within the red blood cells acting as a target for the laser radiation. Suitable optical and thermal parameters could be chosen to define the haemangioma for a range of lasers of interest. Experience with a pulsed dye laser will be discussed. When the user inputs wavelength and pot size, the microcomputer calculates optical and thermal distributions within the tissue, and indicates the appropriate laser energy. The significance of spot size and incident energy density can thus be assessed for a range of treatment modalities. The computer is interfaced to a scanner assembly which automatically irradiates the entire port wine stain with the dosage previously determined. Experience with this unique system based on an inexpensive microcomputer will be discussed.

Effective removal of Port Wine Stain vasculature requires two mechanisms: coagulation of the blood and denaturation of the vessel wall and the surrounding dermis. In this way recanalisation of the old vascular network is prevented and substitution by a normal vessel matrix can occur. A theoretical model was developed to calculate the optiirtuin laser parameters to achieve this. A Monte-Carlo based optical niodel describes the distribution of the laser energy after scattering processes. This distribution is then used by a twodimensional thernial model to predict the temperatures achieved both within the vessel and in the peri-vascular dernds. The predicted effects of various power densities and pulsewidths for 577nit and 585nm will be presented.

Flashlamp excited dye laser therapy represents an exciting new advance in the treatment of a variety of cutaneous vascular lesions. Portwine stains, angiomas and telangiectases can be treated in all age groups with this laser system. This paper will review the physics of flashlamp dye laser photothermolysis. The differences between argon laser photocoagulation and flashlamp excited dye laser therapy will be reviewed.

Continued iraprovement in the results of laser treatment of portwine stain (PWS) , with reduction in scarring, will depend on the ability to use lasers to induce selective injury of only the abnormal blood vessels in the dennis . Photodynamic therapy (PDT), using an exogenous photosensitizing drug specifically activated by a certain wavelength of light, may be used to destroy selectively certain targets in biological systems. The current study demonstrates, in the chicken comb animal model, that PDT using porphyrins and phthalocyanines activated by red light could be used to treat hypervascular derinal tissues.

An argon-pumped tunable dye laser tuned to 585 nm was used to treat clinically typical cherry angiomas in a preliminary study. A spot size of 0.1 mm and low power (0.1 - 0.15W) in the continuous mode was used for treatment. Results ranged from decrease in size of the cherry angioma to complete regression. In all cases, there was minimal to no scarring. Further study in the treatment of elevated cutaneous vascular lesions with the continuous wave dye laser seems warranted.

Laser sclerosis (photosclerosis) of veins after injection of wavelength-specific dyes to enhance and localize energy absorption could provide a useful adjunct to current treatment options. To enhance the absorption of 808nm diode laser energy, ear veins of 18 rabbits were infused with 2-3cc of indocyanine green (maximum absorption 805nm) and exposed for 2 to 20 seconds. Animals were sacrificed between 0 and 28 days after operation. Discrete time intervals of laser exposure exist during which various sized vessels can be photosclerosed without significant thermal injury to the overlying tissue. The use of low power, diode lasers, in conjunction with wavelength-specific dyes, may provide a simple, effective, and cosmetically appealling alternative to current treatment options for superficial varicosities of the extremities.

Superpulsing the carbon dioxide laser allows delivery of high energy pulses separated by short pauses during which tissue cooling can occur.1 This new technology can provide several important advantages in cutaneous surgery over similar procedures performed with conventional continuous discharge carbon dioxide laser systems. In the excisional mode, there is a two-thirds reduction in thermal necrosis of the wound edge.2 This should translate into more rapid healing3 and increased rate of gain in tensile strength. In the vaporizational mode, precise, superficial and bloodless ablation of multiple benign appendigeal tumors is possible with less thermal damage yielding excellent cosmetic results. The establishment through additional research of accurate laser parameters, pulse duration, peak energy levels, and frequency of pulses, will help improve the specificity of the laser-tissue interaction to provide even better surgical results.

Tattoos are physically painful to receive, socially painful to bear, and until now have been painful to remove. The processes used to remove tattoos are an unpleasant catalogue of destructive techniques that produce far less than acceptable cosmetic results.

The laser ablation characteristics of the procine menisci by the various laser irradiations were studied. We employed nine laser wavelengthes from ultraviolet(UV) region to infrared(IR) region, pulsed or continuous wave(cw). They were ArF(193nm in wavelength, pulsed), KrF(248nm, pulsed), XeC1(308nm, pulsed), XeF(351nm, pulsed), Ar ion UV(351nm,cw), Ar ion visible(515nm, cw), Nd:YAG(1.06pm, cw), C0(5.3pm, cw) and C02(10.6jim, cw) lasers. All laser irradiation experiments were performed in vitro with a fixed laser beam to the menisci in air circumstance. The ablation rate and damaged layer thickness were measured. In order to compare the ablation characteristics of various laser wavelengths at the same condition, the laser irradiation energy density was kept constant to 60,J/cm2/sec. The ablation rate by the energy density of 1J/cm2 and the damaged layer thickness by the energy density of 1200J/cm2 were measured. The measured menisci ablation rate by ArF excimer laser was 9.5 (ArF 9.5), (KrF 92.1), (XeCl 74.4), (XeF 2.3), (Ar ion UV 64.8), (CO 69.5), (CO2 204.9) )ig/J. The damaged layer thickness of menisci by ArF excimer laser was 119 (ArF 119), (KrF 12), (XeCl 299), (XeF 645), (Ar ion UV 860), (CO 1105), (CO2 1209) pm. This study will investigate if the ablation characteristics depends on the wavelength of lasers and on emission mode (pulsed or cw). In the case of XeC1 excimer laser irradiation experiment, the contact irradiation to menisci in the water circumstance were carried out. The ablation rate using XeC1 excimer laser in water by the contact method was almost equal to that by the non-contact method in air. The damaged layer thickness using XeC1 excimer laser in water was considerably thin compared with that by the non-contact method in air. We expect that this study for menisci laser ablation may be contribute the progress in arthroscopic laser meniscectomy.

Of all the capabilities of holography for image processing and measuring purposes, holographic interferometry has found the broadest application in biological and medical research. As a technique, which is non-destructive and allows for high resolving deformation analysis, holographic interferometry has gained popularity over the recent years in experimental biomechanics and orthopaedics. Some examples of holographic interferometry in experimental orthopaedics are reviewed in this report. The possibility of using holographic interferometry to study the behaviour of broken bones supported by fixing devices is pointed out in this review.

Orthopedists have been among the last of the specialists to utilize lasers in surgery. Even today, laser usage in orthopedics is almost exclusively limited to arthroscopy procedures. Although other types of lasers have been approved for use in orthopedics, nearly all laser-assisted arthroscopic procedures have involved the carbon dioxide laser in the knee. These techniques involve skills and problems not previously encountered. In an attempt to simplify the usage and circumvent some of the problems, we describe a means of laser energy delivery through the arthroscope.

The laser is used less in orthopaedics than in any other medical specialty. Improving technology and the impressive effect of the CO2 laser on orthopaedic tissues has, however, accelerated the interest of orthopaedic surgeons over the past two years. The carbon dioxide laser is now commonly used in orthopaedics for difficult to access lesions of the knee - particularly those of a degenerative nature with high surface area and low volume. The results are presented in this paper and reveal no evidence of lasting complications. Although several types of lasers are being experimentally utilized in orthopaedics, the YAG and CO2 lasers are the only lasers commonly utilized. The YAG laser is utilized for shoulder arthroscopy and offers the advantage of passage of energy through fiber and the ability to utilize the tool in an aqueous environment. It is too early to determine as to whether or not the YAG laser or the CO2 laser will be the most efficient energy delivery system for use in the shoulder.

The use of laser energy for arthroscopic surgery of the meniscus has been fraught with difficult problems which include excessive tissue penetration and the need for a gas medium. The use of the Neodynium : Yttrium Aluminum Garnet (Nd:YAG) laser offers better control of the penetration depth as well as the opportunity to operate the laser in a liquid medium. Twenty-two excised menisci and twenty cadaver knee menisci were exposed to contact Nd:YAG laser radiation of a power density at 1 .064 microns. The operating parameters included a range of power levels of 5 to 60 watts and exposure time of 0.5 to 1 0.0 seconds. The laser-induced dissection yielded reproducible layers of cavitation and necrosis, proportional to the power and duration of the beam. Carbonized debris was noted on the edge of the cut surface, particularly at the higher power setting. The more peripheral zone of coagulation remained at constant depth and width when tested within the parameters noted above. The Nd:YAG laser has been observed to section the meniscus cartilage in a very controlled, accurate and safe fashion. For the best tissue effect, impulses of 1 5 - 20 watts applied for 2-4 seconds offer the most efficacious combination for the knee menisectomy. While these findings are promising for the clinical utilization of Nd:YAG laser in arthroscopic surgery, additional work is required on both the technical aspects of the sapphire tip design as well as the longterm sequellae of the laser treated cartilage.

Orthopedic Surgery is that surgical discipline which deals with the musculoskeletal system. Orthopedists therefore operate on joints, the spine and long bones and engage in such subsecialities as sports medicine, hand surgery, trauma surgery, and joint replacements. Since they must cut and shape bone, cartilage, tendon, and ligament, orthopedists have developed a number of mechanical techniques to achieve these ends and surgical lasers have found few applications in orthopedics because until now they have not been useful for cutting bone. In the past several years, however, there has been considerable interest in several areas within the field of orthopedic surgery that do not entail actual bone surgery and it is expected that as newer and more powerful lasers become available laser osteotomy may become feasible and even routine.

Recent basic science studies (5) have provided a scientific foundation for the use of the Contact Nd:YAG Laser as an arthroscopic tool for xneniscal resection and acroxnioplasty of the shoulder in a saline medium. This study prospectively evaluates the results of a three stage laboratory investigation as well as the clinical results of arthroscopic xneniscal resection. Fifteen patients with meniscal tears underwent subtotal meniscectomies utilizing a Contact Nd:YAG Laser (Surgical Laser Technologies; Malvern, Pennsylvania) . This was done in a saline medium with an average laser wattage of 25 W, (range 20 W to 30 W). Patients were evaluated postoperatively with reference to subjective and objective parameters at one week and four weeks postoperatively. Patients were evaluated with regard to wound healing, intraarticular swelling and pain. Assessment of technical parameters such as ease of resection, time of resection and instrument access were compared to conventional instruments. All fifteen patients were rated as having clinically excellent results based on pain relief, wound healing and swelling. In addition, although there was increased time with setting up the laser and calibrating it, there was not an increase in time for meniscal resection. Little, or no, secondary "trimmuning" was necessary with the laser. Increased accessibility was noted due to the small size of the laser. Arthroscopic Contact Nd:YAG Laser surgery is a safe and effective tool for menisca]. resection and coagulation in arthroscopic acromioplasties. It provides significant advantages over conventional cutting instruments with regard to accessibility and reduced need for secondary instruments.

Tumors of the brain cannot only, by malignancy, kill patient, but also by their location. These "inoperable brain tumors" have been treated so far by interstitial brachy therapy. For us, this has been a situation for challenge throughout the years.

We embarked on a project to determine the feasibility of treating carotid artery stenosis with the laser and the clinical results of recanalizing peripheral arteries as a "by-product" of these studies. On the other hand, we present a 4-year follow-up of nearly 300 percutaneous disc denaturations in siatic pain patients. Both methods minimize traditional surgical procedures.

Image guided stereotaxis is an accurate and safe method of directing therapy to target volumes define'd in two-dimensional (2D) multiplanes or three-dimensional (3D) perspectives using computer reconstruction of image data. The major limitations of stereotactic techniques are related to a lack of intraoperative visualization and direct monitoring of the procedures and to changes of intracranial coordinates after decompression of cystic lesions or aspiration of cerebrospinal fluid in the management of intraventricular lesions. Endoscopic laser stereotaxis (ELS) involves integration of rigid-flexible endoscopy and Nd-YAG laser to 3D-2D multiplanar image-guided stereotactic procedures (7). The major advantages of ELS include: direct intraoperative visualization, hemostasis, evacuation or resection assessment, and wide exploration of intracranial cavities or ventricles. The technique allows safe aspiration, biopsy, and resection or internal decompression of deep and subcortical intracranial lesions. ELS has proved to be safe and effective in the management of 72 clinical cases and appears to be a promising technique in the management of cystic and intraventricular lesions.

Several techniques have been utilized for intraoperative monitoring of regional cerebral blood flow (rCBF):Xenon-l33 injection technique,therma diffusion flowmetry and Laser Doppler. The results obtained intraoperatively by Laser Doppler flowmeter on 145 patients are analysed and discussed.

Multidimensional tomographic image processing can be used to provide the surgeon useful information on volume, size, shape, location and anatomical relationships of intracranial lesions. Using a reference system this information can be used to "simulate" and interactively optimize surgical treatment. Finally, this computer generated data can be transposed accurately on the "real" physical world or can be used to drive instruments such as microscopes, lasers, etc., leading to automation of neurosurgical procedures. The final goal is the optimization of surgical resection of intracranial lesions.

Effect of low-level laser irradiation on the central nervous system transplantation is reported. Ernbryonal brain allografts were transplanted into the brain of 20 adult rats and peripheral nerve graft transplanted into the severely injured spinal cord of 16 dogs. The operated wound of 10 rats and 8 dogs were exposed daily for 21 days to lowpower laser irradiation CW HeNe laser (35 mW, 632.8 run, energy density of 30 J/cm2 at each point for rats and 70 J/cm2 at each point for dogs). This study shows that (i) the low-level laser irradiation prevents extensive glial scar formation (a limiting factor in CNS regeneration) between embryonal transplants and host brain; (ii) Dogs made paraplegic by spinal cord injury were able to walk 3-6 months later. Recovery of these dogs was effected by the implantation of a fragment of autologous sciatic nerve at the site of injury and subsequently exposing the dogs to low-level laser irradiation. The effect of laser irradiation on the embryonal nerve cells grown in tissue culture was also observed. We found that low-level laser irradiation induced intensive migration of neurites outward of the aggregates 15-22 The results of the present study and our previous investigations suggest that low-level laser irradiation is a novel tool for treatment of peripheral and central nervous system injuries.

The effect of Low Energy Lasers Irradiation (LELI) from green (570nm) cw HeNe laser, red (632nm) cw HeNe laser and pulsed I.R. lasers (904nm) at 950Hz and 4500Hz, on the peripheral nervous system, was examined. The sciatic nerve in rats was surgically exposed, crushed and then subjected to direct irradiation of each laser. It was found that both HeNe lasers significantly boot the electrical activity of the injured nerve, the green (570nm) HeNe laser being more effective. On the other hand, no effect on the electrical activity of the nerve was found with the I.R. lasers. In the second part of this work we made an attempt to explain the phenomenon of low-laser tissue interaction. We found, by an E.P.R. (Electron Paramagnetic Resonance) technique, that singlet oxygen is produced during the irradiation. Singlet oxygen in small amounts is very significant in biochemical processes and hence can be important in biostimulation. It is proposed that singlet oxygen is photoproduced by the natural porphyrins existing in every cell.

Over the past ten years there has been an increasing interest in the use of lasers for neurosurgical and neurological procedures. Novel recent applications range from neurosurgical procedures such as dorsal root entry zone lesions made with argon and carbon dioxide microsurgical lasers to pain relief by low power laser irradiation of the appropriate painful nerve or affected region1 '2 However, despite the widespread clinical applications of laser light, very little is known about the photobiological interactions between laser light and nervous tissue. The present studies were designed to evaluate the effects of pulsed Nd:YAG laser light on neural impulse conduction and axoplasmic transport in sensory nerves in rats and cats. Our data indicate that Q-switched Nd:YAG laser irradiation can induce a preferential impairment of (1) the synaptic effects of small afferent fibers on dorsal horn cells in the spinal cord and of (2) small slow conducting sensory nerve fibers in dorsal roots and peripheral nerves. These results imply that laser light might have selective effects on impulse conduction in slow conducting sensory nerve fibers. In agreement with our elecirophysiological observations recent histological data from our laboratory show, that axonal transport of the enzyme horseradish peroxidase is selectively impaired in small sensory nerve fibers. In summary these data indicate, that Q-switched Nd:YAG laser irradiation can selectively impair neural conduction and axoplasmic transport in small sensory nerve fibers as compared to fast conducting fibers. A selective influence of laser irradiation on slow conducting fibers could have important clinical applications, especially for the treatment of chronic pain.

The effects of subablative Q-switched Nd-YAG laser irradiation on the nerve fiber population of the sciatic nerve in rat were estimated using a quantitative method. The acute and cumulative effects were evaluated separately. When 5-minute laser irradiation was applied to the sciatic nerve, there was a differential decrease in the number of active fibers in slow and fast fiber classes. Fast fibers were insensitive to the radiation as the number of fibers was not altered significantly except at high radiating energies. The amount of decrease in each fiber class was not strictly proportional to the radiating laser energy. The cumulative effects show an exponential decay in fiber number after radiation sequence of gradually incremented laser pulse energy. Similarly, the impairment of fast fiber classes was less significant than slow fiber classes. At high cumulative optical energy, the number of fibers in fast fiber classes started decreasing whereas fiber population in slow fiber classes increased. We postulate that the impairment of the node of Ranvier was the dominant mechanism at lowenergy radiation, whereas the change in the cable properties of internodes resulted in the shift of fast fibers to slower fiber classes.

The application of pulsed or CW infrared lasers to peripheral nerves of mammalian subjects at subablative intensities has shown that action potential propagation is impaired preferentially in slowly conducting axons, and that these laser effects also impair axoplasmic transport over a much longer time period. Parallel studies of afferent processing in the dorsal gray matter of a mammalian spinal cord indicate that synaptic transmission is modified at even lower energy levels. Given that small diameter nerve fibers are concerned primarily with pain transmission, and given further that the superficial regions of dorsal gray matter in the spinal cord are concerned almost exclusively with pain processing, application of infrared lasers to these areas may prove to have short or even long term anesthetic actions.

We have developed a method of fabricating permanently curved hollow metallic waveguides of both constant and tapered inside diameter. This method is based on the use of soluble glass inandrels. In tests with laboratory CO2 lasers we have shown that even without interior dielectric layers these devices can exhibit low loss; e.g., a 22 cm long, 2mm ID guide with a 65° exterior bend transmits more than 90% of properly launched input radiation. We discuss methods of cooling these devices and requirements for their use in neurosurgery.

A new apparatus was designed and constructed for the endoscopic visualization of cavities within the brain. The endoscope was coupled to a very high resolution video camera and monitor to facilitate visualization and provide high resolution visual records. The system has been used safely and effectively in clinical practice. The design considerations, construction, and use of the device are reported.

Since the development of the ruby laser in the early 1960's there has been interest in the area of lasers in dentistry. This interest centered around both hard and soft tissue applications. In the 1970's dentists began using an ultra-violet (UV) light source in the photopolymerization of composite dental materials. Because of the concern regarding the UV light in the mouth a composite resin which activated at 460 nm light was developed. It is intriguing to consider the laser as a better curing light by virtue of the fact that this light is monochromatic, coherent and well collumated. The question this paper has attempted to answer is whether or not laser energy is of benefit in the curing of dental composite resins. A Helium Cadmium (442nm) and Argon Laser (488 nm) were used and compared with a typical dental white light curing unit. Both micro and small particle-sized composites were examined. The results suggest that the lasers tested are not of any great benefit over conventional methods.

Pulsed Er:YAG laser radiation has been found to be effective for dental enamel and dentin removal. Damage to the surrounding hard tissue is little, but before testing the Er:YAG laser clinically for the preparation of cavities, possible effects on the soft tissue of the pulp must be known. In order to estimate pulp damage , temperature rise in dentin caused by the laser radiation was measured by a thermocouple. Additionally, temperature distributions were observed by means of a thermal imaging system. The heat effect of a single Er:YAG laser pulse is little and limited to the vicinity of the impact side. Because heat energy is added with each additional pulse , the temperature distribution depends not only on the radiant energy, but also on the number of pulses and the repetition rate. Both irradiation conditions can be found , making irreversible pulp damage either likely or unlikely. The experimental observations can be explained qualitatively by a simple model of the ablation process.

A system for producing holograms and for three dimensional measurement of dental casts is described. Measurements were performed on a metal testpiece with sharp welldefined contours and on a dental cast. Measurement of the testpiece gave a precision of 0.02 0.11 mm for x, y and z coordinates. Corresponding figures for the dental cast were 0.03 0.43 mm. Precision was higher for the testpiece than for the dental cast, highest for the x and y coordinates and satisfactory for the z coordinates. No difference was found if the hologram was superimposed on the object or two holograms were superimposed on each other. Holograms of dental casts solve storage problems by replacing space consuming models.

Research indicates that laser energy may provide a useful method for glazing and fusing porcelain for intraoral prosthetic purposes. However, it is not known whether such lasing will result in the production of heat levels that may be damaging to adjacent vital tissues such as the dental pulp and periodontal tissues. This research is designed to measure the magnitude of temperature rise across porcelain observed during multiple exposure C02 lasing. Fifteen porcelain examples of 1000 jim (5), 1500 pm (5) and 2000 tm (5) x each received five C02 laser exposures on the same exposure site at 1.0 sec. intervals at 8.0 watts (0.2 sec. per exposure with a 1 mm focal spot). A YSI 144201 thermilinear precision thermistor was placed on the porcelain surface opposite each laser exposure site. Temperature rise above ambient was recorded by an HP3421A data acquisition unit and HP9816 technical microcomputer. Recording continued for sufficient time to allow temperatures to return to ambient. The mean temperature elevations ranged from a low of 2.97 0C (2000 pm) to a high of 7.77 °C (1000 μm). ANOVA and Duncan's Multiple Range Test indicated significant differences in temperature rise by porcelain thickness. It would appear from the results of this research that temperature elevations adjacent to lased porcelain may be sufficiently controllable that safe intraoral porcelain lasing will be possible.

The literature increasingly indicates that lasers will have a multitude of applications for dental hard tissue procedures, e.g. preventive therapy, caries removal, laser etching and endodontic therapy. However, it is critical that such laser therapies avoid the production of heat levels which will be damaging to the surrounding vital tissues, such as the dental pulp and periodontal tissues. Our preliminary research on temperature changes across C02 lased dentin indicated that for single preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot) the mean temperature rise across 350 j.tm of dentin was 0.57 0C while across 1000 .tm of dentin the mean rise was only 0.18 °C. Further research utilizing multiple preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot, 3 x 1.0 sec. intervals) showed mean temperature elevations of 1.56 0C across 350 m of dentin and 0.66 O across 1000 xm of dentin. While these temperature elevations, which would be associated with preventive therapy, are very low and would be biologically acceptable, it must be noted that exposures of higher intensities are required to fuse enamel and porcelain, or remove decay. This current research investigates temperature elevations which occuT during C02 lasing utilizing the following exposure parameters: 8.0 W., 1.0 mm focal spot, 0.1 sec. exposures, 2 or 4 exposures per site pulsed 1.0 sec. apart. Three dentin thicknesses were utilized, i.e. 1000 jim, 1500 p.tm and 2000 .tm. Four sections of each thickness were utilized with four exposure sites per specimen (2 with 2 exposures, 2 with 4 exposures). All dentin sections were prepared from non-carious third molars using a hard tissue microtome. A thermistor was placed on the dentin surface opposite each lased site and temperature changes were recorded for approximately 50 sec. following lasing. Mean temperature elevations ranged from a high of 3.07 C for the 1000 xm section utilizing four exposures to a low of 0.37 0C for the 2000 m section utilizing two exposures. Analysis of Variance (p < .0001) and Duncan's Multiple Range Test (p =.05) indicated significant differences existed among the mean temperature elevations observed. While significant differences in temperature elevation can be observed both by numbers of exposures and by dentin thickness, it would appear that, under the conditions of this study, the temperature changes across CO2 lased dentin are all relatively low. It should be reiterated that the lasing parameters used in this study are far in excess of those necessary for preventive applications and are, in fact, in the range of exposures which will fuse enamel and dental porcelain, or remove dental caries. The modest temperature elevations observed, combined with the relatively severe exposure parameters utilized on thin sections of dentin, demonstrate the effective protective barrier which dentin provides for the dental pulp relative to heat damage from C02 lasing.

The application of lasers in dentistry is not a new concept. Lasers have been used in various areas of dental research over the last two decades. However, recent technological development and research findings indicate that widespread clinical application of lasers will occur shortly. Many of the early studies discovered that high levels of laser radiation were detrimental to the vitality of the dental pulp. This has led researchers to investigate whether low level laser radiation would have positive effects on the various components of the dental hard tissues. This study examined the anti-carious effect of low level C02 laser radiation on smooth surface enamel. Fifty extracted third molars were selected and covered in acid resistant varnish except for two windows on the buccal surface just above the CEJ. The windows measured 1.5 x 1.5 mm with one window designated as the control and the other experimental. In each experiment the Pfizer Model 10-C laser system was used. The teeth were divided into two groups. In group I, the experimental window was lased with 1.2 watts at 0.1 seconds with a 1.5 mm focal spot. In Group II, the experimental window was lased with 2.4 watts at 0. 1 seconds with a 1.5 mm focal spot. Both groups were exposed for 12 days in a demineralizing solution (2.2 mM Ca, 2.2 mM P0 ,50 mM acetic acid, 5 ppmF-@ constant pH -4.3). The resulting lesions were sectioned to approximately 80 im thickness using a hard tissue microtome. Each section was examined by taking polarized light photomicrographs after imbibition in H20 medium. Results of the study suggested a significant reduction in the lesion size in both experiments, all exposures being within the biological safe zone of temperature elevation to the surrounding vital tissues, e.g. the dental pulp and periodontal tissue. Further research will be required to determine the level of CO2 laser radiation which will provide the maximum anti-carious effect.

Polarisation microscopic and SEM investigations of the ejected material following Er:YAG laser radiation on teeth were performed. Depending on the radiant energy different textural structures of material are found. At radiant energies exceeding 50 mJ a melt with crystalline microparticles on the surface can be seen. Supporting our previous hypothesis of the ablation process, now it can be stated, that first the evaporation process will start and with a little time delay some microexplosions with ejecting crystalline material will take place. This is in conformity with X-ray diffractometric investigations. For CO2 laser ablation only a melting deposit was found.

In the field of periodontics and oral surgery, the laser is a relatively new, but rapidly emerging, surgical tool. In the new area of soft tissue surgery, i.e., benign lesion and growths, the laser can completely replace the scalpel and offer the periodontist and the oral and maxillofacial surgeon a new and exciting alternative.

Previous studies have suggested that pulsed laser energy can enhance the bond strengths to dentin of certain dentinal bonding agents. The objective of this study was to investigate and compare the shear bond strength of Scotchbond 2 dentin adhesive (3M) to continuous-wave carbon dioxide laser-irradiated vs. unirradiated dentin. Forty extracted molars were mounted in an acrylic base with the crowns exposed. Dentin surfaces of diameters greater than 5mm were cut perpendicular to the base of the acrylic, treated for 60 seconds with dentin primer, air-dried, and randomly distributed into two groups. The experimental was exposed to CW-C02 laser irradiated at 13.5W for 0.10 sec., and a spot diameter of 5mm. The other group served as the nonirradiated control. A brass ring of 4mm internal diameter was placed on each surface and filled to a depth of 1.0mm with SB 2 and cured. P-50 (3M) composite was condensed and cured into the rings in three one-millimeter increments and then shear strength tested on an Instron machine using a crosshead speed of 0.005 in/mm. The mean shear strength and strain values for the irradiated and control group were 2. 193 MPa, 3.87 x i03, 1 .023 MPa, and 3.3 1 x iO, respectively. Pillai's Criterion and the Univariate F-test indicated that the mean shear strengths were significantly different (p=O.Ol49). These results suggest that dentin bond shear strengths may be enhanced by CWCO2 laser pretreatment.

Enamel and dentin samples were exposed extraorally to a pulsed neodymium yttriuma1uminumgarnet (Nd:YAG) laser. The lased samples were observed using both scanning electron microscopy and histological techniques to determine the effects of the laser. The present study has provided the following points: (1) Properly treated, enamel can be 1aser etched to a depth comparable to that achieved with phosphoric acid etching; and (2) both carious and noncarious dentin can be vaporized by the Nd:YAG laser. No cracking or chipping of any enamel or dentin sample was observed histologically or under the SEM.

The application of lasers in dentistry and particularly for the removal of caries has been proposed for many years. In this paper, the application of lasers in dentistry for hard tissue only is discussed. As a first step, laser drilling of healthy enamel and dentin was performed with most of the potentially interesting lasers available for this application. Among the tested lasers, pulsed lasers with pulse duration in the microsecond range appeared to be the most appropriate (Nd-YAG and flashlamp pumped dye laser [FPDL]). On the contrary, cw-C02 lasers, even at low power, induce only thermal damage and no drilling is obtained. Preliminary results obtained with a long pulse XeCl excimer laser reveal low ablation rates.

Formation of dental cavity may be improved by using a laser beam. This provides nonmechanical contact, precise location of cavity, rapid processing and increased hygienity. Further examination of interaction mechanism is needed to improve the application of lasers in density. Present study examines the tenperature rise and thermal stress development in the enamel during Nd YAG laser irradiation. It is found that the stresses developed in the enamel is not sufficiently high enough to cause crack developed in the enamel.

We have proposed the use of MRI for monitoring and control of interstitial laser surgery, in order to improve the accuracy and reduce the invasiveness of these procedures. To expand the knowledge base about the MR appearance of laser-induced tissue damage, we applied MR imaging and phosphorus-31 MR spectroscopy to detect the changes induced in various tissues by radiation from an Nd:YAG laser at 1060 nm wavelength delivered interstitially through a fiber optic waveguide. A range of laser energies was applied, and laser pulse parameters were varied. Proton MR images of the laser-produced lesions were compared with the histological appearance in brain and liver tissue of experimental animals. The spatial extent of laser effects differed among tissue types, and this was well reflected on MR images. The distribution of MR signal change resulting from different laser exposures was also demonstrated. Experimental laser surgery was performed in animal brain and bladder. Images taken before, during, and after laser irradiation allowed us to distinguish between reversible thermal and permanent effects. This information was utilized to tailor the destruction of preselected targets while minimizing damage to surrounding tissues. Qualitative changes were also revealed on phosphorus spectra. Irreversible lesions were characterized by overall line broadening and a decrease in AT?. There was also a large relative increase in the inorganic phosphate region of the spectrum. These demonstrations are a big step toward achieving our ultimate goal, the development of MR-controlled laser surgery.

A video system is being developed to allow the detection of cancerous lesions that are too small to be accurately identified visually or with x-ray. The system makes use of standard endoscopes and provides a video display of both the color image and a false color fluorescence image, with automated switching between the two views. Excitation of the fluorescence marker, Heinatoporphyrin Derivative (HpD) , or it ' 5 purified form , diheinatoporphyrin ether! ester (DHE) , is provided by a krypton ion laser operating in the violet. A brief discussion of fluorescence diagnostic theory and a description of the prototype system, its clinical use , and performance is reviewed.

One of the modern achievements of fiber optic technology is the development of IR (2-20 mm) optical fibers. Several types of such fibers are available now in the General Physics institute due to the works of groups, headed by V.G.Artjushenko and V.G.Plotnichenko . For IR fibers fabrication several materials such as chalcogenide and fluoride glasses, as well as thallium, silver and alkali-metal halide crystals are used. These are 0.3-1 mm diameter fibers with optical losses about 0.1-1 dB/m. Although this parameter is far from ideal it is possible now to use such fibers in diode laser spectroscopy having in mind the rapid technological progress. The main reason for this work was to make the first, experimental iteration to JR diode laser fiber optic spectrometer, to receive concrete experience in manufacturing and exploitation of this device. The present paper is the first short rcport about this work. The development of this device was based on previous experiments on coupling JR diode lasers and fibers1'2.

A commercial excimer laser angioplasty system with emphasis on small size, long lifetime, and operator convenience is discussed. Particular emphasis is given to the laser energy control system that allows calibrated fluences to be easily achieved. The system reported here, along with appropriate catheters, has been used to perform over 100 percutaneous coronary angioplastys.

We present the initial clinical results of the use of the pulsed 2.15 micron thulium-holmium-chromium:YAG (THC:YAG) laser for gastrointestinal endoscopic surgery. This pulsed mid-infrared laser was designed to fit the clinical need for precisely controllable tissue vaporization which can be delivered via a flexible delivery system. We obtained an Investigational Device Exemption from the FDA and in December 1988 we began our clinical program. Using the THC:YAG laser via a flexible fiberoptic endoscope, we have successfully performed vaporization or excision of sessile neoplastic polyps of the upper and lower gastrointestinal tract of 12 patients. Our initial experience has confirmed our expectation that this new laser system can provide the endoscopic surgeon with a technical alternative not matched by currently available laser systems.

There are substantial technical problems attendant to the removal of sessile polyps from the lumen of thin walled gastrointestinal organs such as the colon. A laser system which is capable of precise and circumscribed mucosal tissue vaporization would be useful for this task. Because of technical shortcomings of existing medical laser systems, we investigated the possibilities of mid-infrared lasers which could take advantage of large water absorption peaks in the 2 micron region to produce precise vaporization while retaining fiberoptic transmissibility. In addition to a high absorption wavelength, pulsed energy delivery contributes to precise vaporizing capabilities. The laser system that best fits our criteria is the 2.15 micron thulium-holmium- chromium:YAG which produces 200 microsecond pulses of energies up to 1 joule at firing rates up to 6 Hz. The laser output is transmitted efficiently via low hydroxyl quartz fibers. Ablative efficiency, defined here as the slope of the vaporization depth versus energy, reveals that the THC:YAG produces approximately 3 times greater depth of vaporization per joule than the cw Nd:YAG. On average, the Nd:YAG produced 1.5 times the amount of thermal damage as the THC:YAG for a given depth of vaporization. The THC:YAG laser should have an important clinical role since its use could reduce the risk of perforation in endoscopic laser procedures such as the removal of sessile polyps.

The paper presents the structure and the set of basic parameters of two laser systems for medical applications in ophthalmology, angioplasty and diagnostics and therapy of tumors. In both systems the basic unit is an excimer laser elaborated and manufactured in the JPPLM.

The use of the laser for applications in electronics, industry and medicine is growing at a rapid pace. Dental applications for lasers, developed to date, have primarily been used for surgery on soft tissues. The pulsed output of the 308 nm excimer laser and the photochemical rather than photothermal action offers the ability to cut on dental structures with minimal generation of heat. In a previous study the action of the 308 nm excimer laser on dental enamel was demonstrated. This study showed that a hole of controlled diameter and depth could be produced. The study has now been extended to determine the effect of the 308 nm excimr laser on dentin. Energy densities of 50, 70 and 90 mJ/mm' were used while exposing points on the dentin surface 500, 1000, 1500, 3000 and 4000 pulses (each 100 pulses equal to 5 seconds time). Tooth samples were rigidly fixed in position while the laser beam was transmitted to the dentin surface through a uv-grade fused silica fiber optic light guide, 600 microns in core diameter. Results showed that a symmetrical hole could be produced in the dentin surface, accurately controlling diameter and depth of penetration. Further results demonstrated that the dentin smear layer was removed and the dentinal tubules could be sealed with the 308 nm excimer laser.

Despite technical advances, the incidence of anastomotic leaks in elective colorectal surgery remains around 14%, Recent studies suggest that the use of low energy lasers may enhance wound healing in different tissues in a selective, nondestructive manner. Based on these findings we have attempted to provide experimental background on the histological effects of He-Ne laser during the early stages of healing in 70 colonic anastornoses performed on rats, The irradiation of the anastomoses by two doses of 3.6 J/cm produces an increase in the populations of round cells and fibroblasts of the scar tissue, an increase in new vessel formation and a significant improvement in epithelialization. This suggests that the irradiation of colonic wounds with He-Ne lasers can result in an enhancement of healing.