A Synthetic WaveFront Interferometer (SWFI) technique has been developed that when utilized can provide simultaneous refraction, pachymetry and keratometry measurements from a single instrument. The corneal topography and thickness measurements are provided globally, i.e., as a continuous measurement over the entire corneal region. The technology involves the utilization of three distinct illumination wavelengths that provide strong separable reflections from the epithelial, endothelial and retinal regions of the eye. Synthetic wavefronts are developed by the impingement of the spectral wavefront containing the phase information onto a single1Ronchi grating (ruling) after reflection from the respective surfaces. Moire patterns (or, SWFI patterns) are produced when these wavefronts impinge on a second Ronchi grating. Computerized analysis of the patterns provide the respective measurements in a clinically usable form. The instrument is not sensitive to mechanical shock, vibrations or misalignment. Thus, it is totally compatible with clinical use.

A Synthetic WaveFront Interferometer (SWFI) technique has been developed that when utilized can provide simultaneous refraction, pachymetry and keratometry measurements from a single instrument. The corneal topography measurement is provided globally, i.e., as a continuous measurement over the entire corneal region. The technology involves the utilization of a distinct illumination wavelength that provides strong separable reflections from the epithelial, endothelial and retinal regions of the eye. Synthetic wavefronts are developed by the impingement of the blue spectral wavefront containing the phase information onto a single Ronchi grating (ruling) after reflection from the respective surfaces. Moire patterns (or, SWFI patterns) are produced when these wavefronts impinge on a second Ronchi grating. Computerized analysis of the patterns provide an image to track in a clinic, or upon use in a Heads Up Display (HUD) system. The system is not sensitive to mechanical shock, vibrations or misalignment. Thus, it is totally compatible with the above uses.

Specular reflections from the inner limiting membrane of the retina of ,llonkeys and from the posterior surface of intraocular silicone oil in patients were studied by the non-invasive technique of imaging fundus reflectometry. Small area of each reflex were measured and the compo ent of reflectance due to the reflex alone was isolated by subtracting the reflectance of a nearby reflex-free area. The reflexes are interpreted as specular reflections at a sillooth boundary between two dielectric media of differing refractive indexes. The reflectances obtained are consistent with the generally accepted refractive indexes of 1.336 for vitreous and 1.36 for retina.

A technique of corneal surgery that is thermally induced and relatively nonenvasive has been studied by the authors, and the preliminary results of the thermal keratoplasty performed on live rabbits are reported here. A carbon dioxide laser was used with simple optical and pointing systems to thermally induce several arbitrary patterns of corneal reformation. Endothelial photographs were taken before the procedure and then again ten days after. They indicated no damage in the Descemet's membrane nor was there damage observed to the endothelium. As much, as 14 "diopters" of change occurred in the corneal keratometry with both positive and negative directions signs. The magnitude and direction of the change were recorded as functions of the pattern of the therapy produced and the laser energy deposited in the stroma. Any corneal reformation was tracked as a function of time subsequent to the procedure. A-minor decay was observed within the first three days of the procedure and the majority of the reformations have maintained at the time of this writing. Since radiation at this wavelength is highly attenuated and absorbed in cornea, no change was observed beyond mid-stroma and the lens and retina appeared uneffective. The authors believe that this technology will be a significant contributor to corneal refractive procedures in the near future. Unlike any refractive surgery currently practiced, this technology may lead to a procedure that: 1) is reversible, 2) is re.eatable, 3) stren thens rather then weakens the cornea, 4) is a..arentl more stable, 5) is more flexible in the types of corneal curvature changes it can produce, 6) results in very clean mires, 7) is painless, and 8) results in total corneal clarity.

Ablation of cataractous human eye lens tissue with carbon dioxiqe laser beam of wave-length 10.6 μm is investigated at power densities upto 20 KW/cm² with interaction time in the rnge of 4-20 msec. It is found that the ablation initiates at a fluence of about 26 J/cm² and thereafter the ablated volume of the tissue increases with the laser fluence with a decreasing slope. A well defined zone of coagulation necrosis borders the laser ablated region and its width increases with the power density and interaction time of the laser beam. From the thermal behaviour of the cataractous lens tissue, it is found that at the onset of ablation, tissue attains a temperature of about 270°C. To confine this temperature to a reasonably small volume, short duration laser pulses will be ideal for ablating the cataractous lens.

Rose bengal is an effective photosensitizing agent which interacts with argon green light to induce photochemical thrombosis of irradiated vessels. We used focal, low energy irradiation to occlude retinal and choroidal vessels in both albino and pigmented rabbits. Immediately after intravenous injection of rose bengal at concentrations of 10 and 20 mg/kg, irradiation was performed via a slit lamp-delivered argon green laser (514.5 nm) with the aid of fundus contact lens. In 11 eyes, arteries were treated with 50-100 interrupted bursts of 75u spot size at 0.2 sec and 40-100 mW (9 <Re <34 KJ/cm²)' and veins were treated with 30-100 bursts of 100u spot size, 0.2 sec, 50-100 mW (5 <Re <19 KJ/cm²) which resulted in total closure of retinal vessels for 1-12 days and variable closure of the surrounding capillaris. Eight eyes were treated with continuous irradiation 2-5 minutes at 7.5-40 mW, 75u spot size (35 <Re <273 KJ/cm²) to arterioles and 2-3.5 minutes, 7.5-40 mW, 100u spot size (12 <Re <107 KJ/cm²) to venules. These eyes developed massive closure of retinal and choroidal vessels, serous elevation of the retina, and disc neovascularization. In eight eyes choroidal vessels were irradiated with 10-20 mW, 15-60 sec, 500u spot size (31 <Re <306 KJ/cm²), resulting in mild retinal edema at 24 hours and permanent closure of choroidal vessels. There was minimal damage to surrounding tissue. Control eyes in all three groups irradiated utilizing the same parameters, but without rose bengal, demonstrated no evidence of thermal injury.

Tissue fusion using a computerized 1.3 micron YAG laser has been in use in human clinical trails under a FDA investigational device exemption since June, 1988. Animals studies using the 1.3 micron wavelength will be reviewed.

Low power CO₂ laser energy is capable of remodeling collagen through a photothermal process. Methods of CO₂ laser tissue fusion have been developed which permit repair of blood vessels, stomach, small bowel, fallopian tube, and vas deferens. Analyses of these reconstructions demonstrate significant injury in the area of laser impact but minimal injury of the luminal surface. Healing proceeds rapidly. The biomechanics of the laser repair are similar to that of suture repair. Preservation of the luminal surface and function, rapid healing, and the absence of foreign body suggest that CO₂ laser repair may provide a better method of tissue reconstruction.

Two mechanisms of laser tissue fusion, thermal and photochemical, are currently being proposed in several types of tissue. In this study we examined the thermal and histologic components of laser fusion in blood vessels and bowel. CO₂ and Argon lasers were used to fuse 1 cm canine arteriotomies and 1 cm rabbit enterotomies. Thermal images were concurrently recorded with an AGA Thermovision camera and computer analyzed. Tissue samples from each weld were subsequently prepared for histologic examination.

Laser-assisted arterial and venous anastomoses are now possible using a low power CO₂ laser. A microscope-guided CO₂ laser has been used to deliver 60 to 100 mil liwatts to anastomose arteries and veins. This technique has been used to anastomose rabbit carotid arteries (1.5 to 2.0 mm), rabbit femoral arteries (1.1 to 1.5 mm), and rabbit vena cavae (4 to 6 mm). In addition, rat femoral arterial end-to-end (1 mm) and arterial venous fistulas have been completed. Histologic examination of laser-assisted anastomoses showed local full-thickness thermal injury. Repair was by fibroblast and myofibroblast proliferation, and luminal cell coverage was complete by 14 days in laser repairs. Laser arterial and venous anastomoses are attractive because of their simplicity and rapidity of performance. Their patency has proved to be comparable to sutured anastomoses, but arterial aneurysms remain a hazard despite use of extemely low laser energy.

The speed, accuracy and efficiency of using laser energy to fuse together or weld living tissue makes laser tissue welding one of the most exciting areas of medical research today. Numerous investigators using animal models and several surgeons conducting clinical studies have demonstrated many promising potential applications of laser tissue welding. Accurate tissue positioning and well controlled delivery of laser energy during laser welding are essential for consistently successful laser tissue repairs. Many surgical procedures involve the creation of functional anastomoses, which are patent connections between hollow, tubular tissue structures, like bowel, blood vessels or fallopian tubes. We are developing the Exoscope System^TM to automate and simplify the production of laser welded end-to-end and end-to-side anastomoses. Any laser light that can be passed through an optical fiber can be used in this system. The Exoscope System^TM employs a fiber optic Exoscope Device,^TM which provides for the precise placement of laser energy onto the abutted tissue seam, and a biocompatible, dissolvable intraluminal PolySurge^TM stent, which holds the tissue in circumferential apposition during lasing. The feasibility of employing the Exoscope SystemTM technique for the construction of rabbit small bowel anastomoses was successfully demonstrated in a Phase I study comparing 30 Exoscope System^TM laser welded anastomoses to 30 conventional sutured anastomoses.

This article reviews the current state of the art in the field of vascular welding using the milliwatt CO₂ to repair 4 to 9 mm vessels. Previous work in arterial anastomosis and intraluminal welding is evaluated. A preliminary study in the area of venous anastomosis is presented in detail. Following the presentation of the current available data, a discussion of the field will emphasize what we know and what still must be learned. The conclusions confirm the feasibility of laser-assisted vascular repair and highlight its method of coagulative welding with resultant short and long-term effect on living tissues.

Extracellular matrix components from untreated and laser-welded skin and blood vessels were extracted with guanidine hydrochloride and separated by SDS polyacrylamide gel electrophoresis. When compared to matched, untreated tissues, protein electrophoretic profiles from laser-treated samples showed several changes. In both tissue types, the concentration of a protein normally migrating between alpha and beta chains of type I collagen decreased in laser-treated samples. However, laser-treated blood vessels showed significantly more low molecular weight protein, whereas significantly more high molecular weight protein appeared in laser-treated skin samples when compared to untreated tissue. These results suggest that the argon laser either degrades or crosslinks proteins in-vivo. Laser induced protein crosslinks may be the biochemical basis of laser welding.

The first report of laser irradiation for wound healing was done by Mester, E., et al. in 1968. From their reports, we can get many knowledges and suggestions as for laser irradiation. At that time he used ruby laser (694.3 nm wave length) for surgical wounds and burns on the back skin of mice. The condition of irradiation was studied with energy density between 0.5-10 J/cm² twice a week. As a result, they noticed 1 J/cm² irradiation was effective for those wounds. After a few experimental reports, they published their clinical studies in 1975. Clinically, they used He-Ne laser (632.8 nm wave length) irradiation. Human leg ulcers due to peripheral circulatory disturbance were treated with energy density of 4 J/cm² twice a week. And they got good results, obtaining complete healing in two-thirds of the cases. We became strongly stimulated by those reports. We have been studying the effect of light on experimental and clinical wound healing as well as on various kinds of biological phenomena since 1980. Particularly, its effect according to the difference of light has been studied. In October 1982, the first clinical case was tried by Argon laser (514.5 nm wave length) irradiation for therapeutic purpose. A man had a chronic ulcer of the left first toe due to Buerger's disease for 5 months. Surprizingly, on the 14th day after 6 treatments of the light irradiation, his ulcer completely healed. During these treatments, the patient noticed that the pain completely disappeared after 2 treatments. Fifty Argon laser treatments were carried out on clinical cases after these experiences, we reached to a conclusion that light irradiation stimulated something in the injured tissues and lead to good clinical results. Several studies concerning mechanism for these effects i.e. peripheral circulation, histology of granulation, cell proliferation, chemistry and other studies were carried out. From these investigations, peripheral circulation was improved when in those who were suffering from vascular disorders but was not effective in normal subjects. From a study of cellular electrophoretic mobility, irradiated G₀G₁ cells increased their mobility, but irradiated G₂M cells decreased. These results suggested light irradiation contributed to homeostasis of living cells, tissues, and body. Experiments concerning the light sources, i.e. wave length, energy density and polarization were done. As a result, linear polarization and right circular polarization improved wound healing, but incoherent light itself did not. ,According to our studies, no distinguished differences among various kinds of wave length were noticed. And light irradiation with energy density was very effective between 2 to 6 J/cm². We strongly suggest the role of coherency is very important to do light irradiation on the living body. In conclusion, we like to propose our new viewpoint. That is, the light irradiation should be discussed with the structure of high molecular substances in the living body.

We have studied the effectiveness of He-Ne laser (8.5mW) in treatment of rheuma-toid arthritis of totally 77 cases. Placebo irradiation was applied to 32 patients, and He-Ne laser to 45 cases. The length of irradiation was 15 minutes per each treatment. During the experiment period, the assessment to tenderness, pain on motion, circumference, range of motion, grip strength, duration of morning-stiffness, hydrops, and ESR was performed. Thermograph and other laboratory tests were also assessed. The general assessment by the doctors showed significant clinical diffe-rence (P<0.01) in the intergroup comparison. In the assessment of the patients' personal impression, significant improvement was recorded too (P<0.01).

The bio-stimulation effect of semiconductor laser on therapeutic pain relief was investigated by conducting a double blind test performed on more than one hundred patient subjects suffering from various neualgia. A compact laser therapeutic equipment with two laser probes each having 60 mW power was developed and utilized for the experiment. Each probe was driven by either the active or the dummy source selected randomly, and its results were stored in the memory for statistical processing. The therapeutic treatments including active and dummy treatments were performed on 102 subjects. The pain relief effects were confirmed for 85.5% of the subjects.

A low power carbon dioxide laser was used to perform 110 end-to-end laser-assisted microvasuclar anastomoses of carotid arteries in ginea pigs and rabbits. In 56 of 72 cases which were irradiated with power output 20-40 mW, energy density 1.5-2.5 Joule/mm², showed patency immediately after surgery with no wound distruption nor thrombus formation. From these results, the optimum condition for anastomosis seemed to be in this range of power output and energy density. The bursting strength of laser-assisted anastomosis (LA) was assessed and compared with conventional suture anastomosis (CA). LA arteries consistently demonstrated lower bursting strength than those of CA. Relatively low bursting strengths at 1 hour and 3 days in the LA with 3 stay sutures may explain the late aneurysm formation. Additional stay suture seemed to prevent such complication. The mean duration of each anastomosis was 13 minutes for the LA repairs compared to an average of 24 minutes for CA repairs. These findings suggest that a low power carbon dioxide laser has potential clinical application for anastomosis of small vessels.

Pulses of laser light in the 2 micron range should ablate tissue in a manner similar to the 10.6 micron CO₂ laser with the added advantage of efficient transmission through flexible quartz fibers. We performed an evaluation of a pulsed 2.15 micron laser system with regard to the laser's potential for atherosclerotic vascular applications. In vitro, we lasered fresh human calcific atherosclerosis. Approximately 10 pulses of the THC:YAG at 900 mJ/pulse penetrated a 5 mm thick plaque and caused approximately 80 micron depth of thermal damage. For the in vivo testing, fourteen rabbits underwent aortotomy and backwall exposure to 5 pulses of the THC:YAG laser at 450 millijoules per pulse in order to evaluate the thrombogenic and healing potential of 2.15 micron lasered vessel walls. At time of sacrifice, all aortas were patent. Immediately after treatment, a 60-80 micron deep area of dessicated tissue surrounded the lasered crater. A 40 micron thick thrombi covered the damaged tissue. Healing of the lasered tissue consisted of neovascularization and fibroblast ingrowth from the periphery as well as endothelial cell ingrowth from the surrounding intima. Our results indicate that the pulsed 2.15 micron THC:YAG system deserves further consideration for angioplasty applications.

Laser assisted microvascular anastomosis with a variety of lasers has been reported to provide shorter operating times, less tissue reaction and possibly better long term patency rates. We describe our experience using a pulsed thulium-holmium-chromium:YAG laser (2.15 micron) to construct sutureless microvascular anastomoses. The intermediate absorption of this wavelength compared with CO₂ and Nd:YAG lasers, allows uniform heating of the vessel wall. End-to-end anastomoses of 10 rat carotid arteries were created with the THC:YAG laser. Histologic sections of anastomosed vessels confirmed full thickness fusion of the media with minimal thermal damage. Bursting pressures were all in excess of 300 mm Hg. The THC:YAG laser creates vascular fusion of sufficient immediate strength to perform microvascular anastomosis.

Excimer laser is able to destruct tissue with less thermal effect. This characteristics was considered to prevent thermal perforation in laser angioplasty. In order to realize coronary laser angioplasty with excimer laser under the visual condition, the basic studies were performed to evaluate the tissue reactions of excimer laser on atheroma and to develop laser endoscopic system for the coronary arteries. The tissue reactions of excimer laser in atheroma were evaluated with rabbit's atherosclerotic aorta, which was made with 1.5% high cholesterol diet. The bigger tissue destruction was obtained in accordance with the increase of the oscillating frequency. Excimer laser indused rather selective destruction of atheroma with high oscillating frequency. The fiber transmission of excimer laser was tried and atheroma was destructed through 400 μm core diameter fiber. Atheroma was observed as like as small lump under endoscopic obsevation, and excimer laser could be irradiated through the fiber under endoscopic view. In order to realize endoscopic application of excimer laser to the coronary arteries, the endoscope was designed from the point of percutaneous approach method to the coronary arteries, and 1.5 mm diameter of endoscope with the channel for laser fiber was developed experimentally. The endoscope could be inserted deeply into the coronary arteries of goat, and the laser irradiation could be performed under endoscopic observation. The possibility of visual coronary laser angioplasty with the combination of excimer laser and coronary endoscope was demonstrated with the endoscope.

Endovascular damage from CO₂, Nd:YAG, or argon laser can be considerable, causing reduced vascular biosynthesis of prostacyclin and precipitating platelet aggregation. However, the degree of platelet thrombus formation has not been directly quantified. Using Indium labeled platelets, platelet accumulation after low radiant energy CO₂ laser endarterectomy was compared to accumulation after standard microsurgical endarterectomy in normal canine carotid arteries. Undisturbed adjacent segments from the same arteries served as controls. Platelet deposition (Indium activity per minute per milligram arterial tissue) was significantly greater on laser treated segments than on surgical (p=0.002) or control (p=0.002) segments. This confirms prior histologic evidence of increased acute platelet deposition after CO₂ laser endarterectomy and suggests the need for further investigation of the thrombogenicity of laser angioplasty.

This report describes our progress in the development of argon ion laser endarterectomy for arteriosclerotic cardiovascular disease. Nine patients underwent 10 vascular reconstructions for claudication (6), rest pain (1), and gangrene (2). There was 1 aortoiliac endarterectomy, 6 superficial femoral artery endarterectomies, 1 profunda femoris endarterectomy and 2 popliteal endarterectomies. The reconstructions were 6 cm to 60 cm in length. The operations were performed using low power argon ion laser radiation, 1.0 W. All patients experienced symptomatic relief and had palpable pulses postoperatively. There were no perforations and there were no injuries to surrounding tissues from laser radiation. Surgical complications occurred and these were technical problems that should be eliminated from the operation with further developments. The early clinical results show that laser endarterectomy can be performed for peripheral vascular reconstruction using low power argon ion laser radiation.

Laser has made it possible to develop a new technique in surgical intervaentions on the gastrointestinal tract. It is based on a combination of the laser beam with a set of special instruments. It allowed to increase considerably a quality of surgeries and to inprove long-term results.

Laser welding of biliary tissues would be a valuable technique in conventional and endoscopic surgery. Laser welding would allow the avoidance of potentially lithogenic suture material as a sequela to biliary tract surgery. Laser welding would be compatable from the surgical technical standpoint with fiberoptic endoscopic intrumentation. The 2.15 micron thulium-holmium-chromium laser offers tissue penetration on the order of a few hundred microns. We have hypothesized that this laser might be well suited to performing biliary tissue welding. We evaluated this laser in vitro using canine gallbladder tissue and we were able to achieve histologically satisfactory tissue fusion and immediate bursting strengths above physiologically encountered biliary pressures.

There is considerable interest in methods of dealing with gallstones that would be less invasive than traditional gallbladder surgery. Our group has been especially interested in percutaneous endoscopic or transcatheter methods for performing biliary lithotripsy. We performed an in vitro comparison of three methods for lithotripsy, the thulium-holmium-chromium:YAG laser (THC:YAG), the ultrasonic lithotriptor (UL) and the electrohydraulic lithotriptor (EHL). We concluded that no one modality is clearly superior to the others, but rather that these methods are complementary with each modality having a preferred role.

The large-scale radiation-hydrodynamics computer code LASNEX, has been used to model experimental results in the laser ablation and fragmentation of renal and biliary calculi. Recent experiments have demonstrated laser ablation and fragmentation of human calculi in vitro and in vivo. In the interaction, laser light incident upon the calculus is of sufficient intensity to produce a plasma (a hot ionized gas). The physical picture which emerges is as follows. The plasma couples to acoustic and shear waves which then propagate through the dense stone material, causing spall and fracture by reflection from material discontinuities or boundaries. Experiments have thus far yielded data on the interaction against which models can be tested. Data on the following have been published: (1) light emission, (2) absorption and emission spectra, (3) fragmentation efficiency, (4) cavitation bubble dynamics and (5) mass removal. We have performed one dimensional simulations of the laser-matter interaction to elucidate the im-portant physical mechanisms. We find that good quantitative fits between simulation and experiment are obtained for visible light emission, electron temperature, electron density, plasma pressure and cavitation bubble growth. With regard to mass removal, experiment and simulation are consistent with each other and give an excellent estimate of the ablation threshold. The modeling indicates that a very small ablation layer at the surface of the calulus is responsible for significant mass loss by fragmentation within the bulk of the calculus. With such quantitative fits in hand, we believe this type of modeling can now be applied to the study of other procedures involving plasma formation of interest to the medical community.

Laser parameters have recently been optimized to specifically destroy cutaneous blood vessels and at the same time, spare injury to adjacent epidermal and dermal structures such as collagen. When these parameters have been used in clinical treatmeng, it has been observed that electron-lucent spherules of 600-800 Å diameter have consistently been present in these irradiated red blood cells (RBC) producing de-st'ruction of abnormal port wine stain blood vessels. It has been postulated that these changes were due to oxygen released during laser irradiation with the implication that the oxygenated status of the blood affected. the clinical outcome. This study demonstrates that this clinically related RBC morphology is independent of the oxygenated status of the blood. Microspectrophotometric measurements of absorbance across individual RBC of laser irradiated oxygenated and deoxygenated erythrocytes as well as those rapidly heated to temperatures greater than 100°C confirm that these electron-lucent structures are due to a phase change occurring in the RBC and not to oxygen release.

Lasers are an accepted modality in the treatment of various superficial blood vessel malformations. Unfortunately use of the continuous wave lasers such as the argon and argon tunable dye lasers has been limited by the associated risk of scarring which ranges from five to thirty percent. The risk of scarring is greater in people with fine skin such as that in children and in certain more delicate body sites such as the upper lip and extremities. The extremities are a particularly difficult site to treat being more susceptible to scarring.

Laser surgery has become the most frequently used treatment for cutaneous vascular malformations. Unfortunately, using the continuous wave lasers such as the argon and argon tunable dye lasers has resulted in a fairly high risk of scarring, ranging from 5-30% compared to the pulsed light from the flashlamp-pumped dye laser. The flashlamp-pumped dye laser was designed to coagulate vessels about 100 microns in diameter. It is not effective in closing vessels much larger than this. For this reason it is important to have a modality that makes the closure of larger vessels possible without scarring. It is possible to minimize epidermal temperature rise in response to continuous wave light application by the use of a 100 micron spot size focused on the vessel tissue which will restrict coagulation to the vessels. Skin surface temperatures were measured using a thermocouple. When coherent light was delivered from an argon (514 nm) and argon tunable dye (577 nm) lasers, a 100 micron spot power of 0.1 watt and one second exposures were used, the mean skin surface temperature rise was 6 ± 2 degrees celsius. By contrast, a 1000 micron spot, power of 1 watt and one second exposure resulted in a mean temperature rise of 20 ± 2 degrees celsius. These measurements were confirmed using an Inframetrics thermal camera. Treatment of portwine stains using this technique has substantially reduced the incidence of post-laser scarring.

Now, more and more hospitals and doctors in the world are getting interested in laser medicine, more and more people are getting understanding on laser surgery operations and physical therapy. Following the cotinuous comprehensive investigation of laser medicine, the clinical applications of laser has been further expanded and per a lot of indications have been found. As is well known, CO₂ laser is one of the most famous medical lasers. In recent years, we concentrate our at to it, a new minitype CO₂ laser surgery instrument has been built after improving repeately, the improvement depends on the experiences of hundreds of doctors in hundreds of hospitals for curing ten thousands cases. Our new laser surgery instrument has been improved in five-main characters: 1) Expanding the range of adjustable power into 3-10 W; 2) Making the laser output flexible, dose from 0.1--10⁵ W/cm² for different cures; 3) Expanding its applications into about 50 indications of general surgery, dermatology, otolaryngology, and gynecology. Which have been proven effective or very effective.

Since February 1987 to March 1988, 118 biopsy proven basal cell carcinoma were treated in 22 patients at the National Cancer Institute in Milan. The treatment consisted in the tumor photosensitization by topical administration of Tetraphenyl-porfinesulphonate (TPPS) onto the tumor surface, and red light exposure. The irradiation was performed by an Argon-pumped dye laser at 650 nm. The persistence of the lesions was noted in 4% of the cases. 13% of the cases recurred after 4 months. 35% of these recurrences were at the periphery of the irradiated area, and a second, treatment gave complete tumor regression. Important complications did not occurred; only in 3 cases a moderate skin distrophy resulted.

The fate of hematoporphyrin derivative (HpD, 10 mg/kg) was studied with microspectrofluorimetry in frozen tissue slices from female rats. In infact animals we observed the maximal incorporation of HpD in the small intestine mucosa, liver, lung, stomach and blad-der in 30 minutes, and in the skin and kidney - in 6 hours after an intravenous injection. In cancerous organism HpD was usually retained for 6-12 hours in different organs and for 12-48 hours in the tumor. Thanks to this the tumor/organs ratio achieved 2-150 times for tissue concentration and 2-11 times for fluorescent-contrast by the 6th hour after intravenous injection. Thus, the optimal time for experimental studies of carcinosarcoma photodynamic therapy with laser irradiation was found to be 4-6 days after its transplantation and 6-12 hours after intravenous HpD administration.

The results of the treatment of patients with suppurative-inflammatory diseases when lasers were used are presented in this article. The comparision was made between two similar groups: one was treated with laser, the other -without it. After the analysis has been made we came to the conclusion that laswer irradiationfor the treatment of suppurative-inflammatory processes in soft tissues is highly effective and economically beneficial.

Present study examines the interaction of laser beam with the biological structures. Nd YAG laser delivering pulses within 1.48 msec is used while fat, heart and liver cells are selected as specimens. The selection of these specimens is based on their range of optical and thermal properties. It is found that there may be three major zones distinguished for inpreting the effect of laser irradiation on the biological cells experimented.

Transurethral laser destruction using contact Nd:YAG laser (TULD) was performed on 96 occasions in 72 patients from February 1984 to December 1987. For the purpose of cure, TULD was undertaken on 59 occasions in 37 patients with primary bladder cancer. In the 59 occasions, usefulness of the TULD was evaluated. The cancers were classfied and staged in accordance with the Japanese Urological Association. The usefulness of the TULD was judged by surgeons with criteria as follows: degree of difficulty of manipulation, degree of destruction of the cancers, and bleeding during the TULD. Features of the cancers, for which the TULD was judged as useful, were summarized as follows: 1. On cystoscopical findings, the form of the cancer was superficial, the number of cancers were under the number of four and the sizes of the cancers were under 3 cm in diameter. 2. On pathological findings, the grade of the cancers reached grade II and the stage of the cancers reached stage T1.

Photodynamic therapy (PDT) using laser has recently been demonstrated to be applicable for cancer treatment. The combination of Pheophorbide a (Ph-a) and pulsed Nd:YAG laser irradiation has enabled us to perform PDT with the same system as used in laser hyperthermia. We have investigated this new method using human neoplastic cell lines and we calculated the survival rates after laser irradiation. Next then, in order to determine the mechanism of photochemical action we measured lipid peroxide levels of cells and lastly, demonstrated the protective effects against PDT induced by chemical scavengers. We found that pulsed Nd:YAG laser irradiation with Ph-a caused a photochmical action in cell cultures, and active oxygen spieces and/or lipid perxide were likely involved in the photodynamic process.

The contact Nd:YAG laser system with ceramics tip was applied to head and neck reconstructive surgery. Plastic surgery was performed in 78 patients with head and neck diseases during the past 11 years. Since 1984 reconstructive surgery in these patients was made on 60 cases and on 45 cases(75%) of these cases the contact Nd:YAG laser surgery was used. Using this laser technique, half volume of bleeding in the operation was obtained as compared with that of the conventional procedure.

The many and complicated causes of mucosal pathology in chronic naso-sinusitis have been reported during the past 30 years. Great importance is attributed to the sinus ostium, mucociliary function, turbinate pathology and charactristics of sinus secretion. Owing to such inflammatory foctors as shown in Figure 1, there is offen an occluded natural ostium of allergy, trauma or swelled mucosa in the nasal cavity. A blocked ostium facilitates transdation and secretion originated in the sinus mucosa and, consequently, microorganism invation or growth can then take place.

The usefulness of laserthermia using Nd:YAG laser was studied experimentally and clinically to treat deep seated brain tumor. Histological changes, temperature profile, modification of blood-brain barrier (BBB) were studied. Five patients with brain tumors were treated with laserthermia. Laserthermia using Nd:YAG laser is easy and safe to use and it is beneficial to treat deep seated brain tumor. Photodynamic therapy (PDT) was also evaluated using the photosensitizing agent pheophorbide-a (Ph-a) and an acoustic Q switched Nd:YAG laser. In xitro survival of T98G human glioma cells pretreated with Ph-a (1x10^-3 mole/1 in albumin) and irradiated with a pulsed Nd:YAG laser for 5 minutes at 37.0°C was 0.4%. The present study suggested that PDT using an acoustic Q switched Nd:YAG laser and Ph-a was useful in treating experimental human glioma.

Artificial caries lesions were made on the buccal surface of human premolars, and the enamel was then treated with laser and fluoride. The acid resistance of the enamel was examined by demineralization in acidic solution. An increase in acid resistance and fluoride uptake was caused by fluoride treatment after laser irradiation. In addition, remarkable remineralization of artificial caries lesions was seen in these specimens after exposure to calcifying fluid.

It has been difficult to treat chronic otorrhea of post-operative complication following middle ear surgery. Low power CO2 microlaser surgery was applied in 14 cases of infectious chronic otorrher assocoated with radical mastoidectomy of middle ear cholesteatoma. Laser was irradiated at the low level from 1 to 5 watts by defocused beam.Otorrhea was completely stopped in 7 cases and remarkedly decreased in 6 cases. This treatment showed remarkable improvement of infectious region in the middle ear cavity and induced good reepithelization within 3 weeks without any operative complication. This results indicated low power CO₂ laser treatment was very safe and usefull for removal infectious soft tissue as well as wound healing in the opened middle ear cavity compared with conventional treatment.

In 1983, we initiated experimental and clinical studies of endoscopic Nd:YAG laser treatment with SLT contact probes for endoscopy comparing with the non-contact quartz fiber, in order to evaluate the histological effects and safety to each method. The first computer-controlled endoscopic loval hyperthermia (Laserthermia) system was developed and reported at the 6th Meeting of the Japanease SOciety for Laser Medicine in Sep. 1985. We named interstitial local hyperthermia with Nd:YAG laser, "Laserthermia". Recent 3 years, technical and histological studies for treatment of the gastric cancer were carried out and reported in the SPIE's symposium. In this paper, newly developed the single channel method, and histological studies by Laserthermia to the human gastric cancer transplanted to the nude mice were discussed.

A new surgical technique for the Nd:YAG laser, involving irradiation using a balloon filled with a light scattering substance, is described. Applications of this technique to hyperthermia, designated 'balloon laserthermia', were studied. A balloon was attached to the end of the optical fibre, and a substance to scatter the laser light was introduced into the balloon. The laser was activated after the balloon was placed in contact with the tissue. Fat emulsion was used as the scattering substance. From the results of our initial research, it is clear that a 0.25% density of the emulsion is adequate to obtain completely scattered irradiation. The effects of this balloon laserthermia on tumor-bearing mice was investigated pathologically, and more than 90% of the tumor cells in the tumor nodule became necrotic, or showed marked degeneration. As laser hyperthermia becomes possible with this technique over wider areas, we foresee wide clinical applications.

The continuous expanding of CO₂ laser applications in medicine needs not only compact, reliable and multifunctional surgical CO₂ laser units, but also specialized beam delivery systems, which are essential to extend the clinical use of lasers. Our effort for improving the surgical CO₂ laser units was directed to : a) developing compact CO₂ laser scalpels, reliable and more suitable for the surgical operating theatre by using high performance with low maintenance average power sealed-off CO₂ lasers; b) designing specialized electronic circuits to increase the protection degree against uncontrolled irradiation by technical failures or wrong manipulation; c) extending the operating regimes, i.e. continuous wave, laser pulses with pre-established length and laser pulses with variable repetition frequency. The beam delivery systems used with our surgical CO₂ lasers units included opto-mechanical articulated arms, IR fiber optic cables and laser microscope adaptors. Coupling different CO₂ laser scalpels, beam delivery systems and terminals, we have tested these surgical laser units in neurosurgery, otolaryngology,,ophthalmology and microvascular lympho-venous anastomosis. The most significant data recorded by us on the interaction of laser radiation with living matter are shortly reviewed.

Laser ablation and removal of intravascular plaque has long been a goal of physicians and physicists as an alternative treatment for coronary and peripheral artery disease. Early application of cw free light beam visible and infrared lasers such as argon ion or Nd:YAG lasers for this application were plagued by thermal side effects of the ablation process. Specifically, imprecise control of the boundary tissue injury produced by the deep penetration depth of the laser beam gave rise to early reclosure of the vessel due to the thermal nature of the ablation process. Pulsed ultraviolet laser free beam ablation of atherosclerotic plaque, however, does not produce thermal effects, cuts tissue precisely leaving a smooth wall and can ablate hard calcific lesions. We have chosen to develop a XeC1 excimer laser-fiberoptic delivery system for the clinical application of laser angioplasty based on achieving the desired therapeutic results for a laser revascularization procedure. Four major engineering design issues must be considered in order to produce a successful clinical laser angioplasty product. These engineering issues are: 1) Functional clinical engineering, 2) Regulatory design issues, 3) Hospital facility and user requirements, and 4) Economic issues for the manufacturer, the hospital and the patient.

Use of laser radiation in medicine promises new positive results. In the recent years the greatest hopes were associated with application of excimer lasers. However, successful experiments in this field and then clinical trials are possible only if specialized medical lasers are developed. For experiments in angioplasty we have developed a multifunctional device based on the excimer laser which provides a generation of radiation at a large number of active molecules.

Laser photoradiation therapy for neonatal hyperbilirubinemia is a breakthrough in the management of neonatal jaundice. In this paper the authors present a new laser system that provides combined monitoring and therapy for neonatal hyperbilirubinemia. The new system incorporates tunable laser sources that can be operated at selected wavelengths to achieve both transcutaneous differential absorption measurements of bilirubin concentration in addition to laser photoradiation therapy. The new laser system can allow the treating physician to avoid over or under treatment of jaundiced neonates by the control of serum bilirubin from a critically high level to a reasonably safe level.

The feasibility of using acoustic and plasma optical feedback emissions for guidance during pulsed laser lithotripsy and angioplasty procedures was studied in-vitro. A flash-lamp pumped tunable dye laser operating at a wavelength of 504 nm (coumarin green) was used as the laser source. Acoustic signals were recorded with a hydrophone which has a useful frequency response of up to 350 KHz. Plasma optical emissions were transmitted retrograde along the laser fiber and reflected through a beam splitter to an optical detection system consisting of a series of spectral filters (to transmit plasma radiation from 380 to 440 nm and block any 504 nm laser light) and a photomultiplier tube. Measurements of the laser-induced acoustic and the plasma optical emission signals were obtained from urinary and biliary calculi, ex-vivo bovine ureters, blood, blood clots, bile, atheromatous plaque and normal arterial wall. Results of monitoring show that it is possible to know without direct vision whether the laser energy is being discharged in the lumen, on healthy soft tissue, or on calculus or atheromatous plaque. Blood, blood clots, bile produced strong acoustic signals but no plasma signals; calculi and plaque produced strong plasma and strong acoustic signals. Neither plasma nor significant acoustic signals were produced by normal ureteral or arterial wall. These distinctions may allow clinical laser fragmentation of calculi or ablation of plaque to be performed with fewer complications.

Anslysis of spectral fluorescence properties of tissue under laser-induced excitation can be a highly informative method of clinical diagnostics of some diseases of internal organs and a method of examination of their functional state.

Control system design for medical products has been greatly enhanced by the advent of microcontrollers. However, the introduction of software control has given rise to a new class of potentially hazardous, fault-intolerant situations. This paper discusses a system of hardware/software interrelationships which provide for efficient fault tolerant control system design. Medical laser systems under unsupervised, nonredundant (single) processor control are easily designed but are considered unsafe by most regulatory commissions. Redundant (multiple) processor control is considered safe but system development is complicated and hence prohibitively expensive for small scale medical systems. A nonredundant processor utilizing a software kernal and a hardware shell can be easily configured to satisfy regulatory safety requirements. Such a system retains much of the pliancy inherent in software control while adding the simplicity and reliability of hardware safety constraints. The hardware/software interaction forms a hybrid redundancy whereby the software serves to monitor the integrity of the hardware and the hardware maintains operational boundaries for the software. The initial hardware design remains fixed according to system performance requirements. Very little special software is needed to accommodate the hardware constraints and most system operational changes can be made solely via software. This results in a system design which is safe, sufficiently flexible, and economically feasible.

In this study, we have demonstrated that a single foveal lesion can produce suppression of central cone function and increased sensitivity of parafoveal receptor systems that might be adjacent cones, partially functional long wavelength cones, or normally suppressed rods. Passive and active movement of receptors during the repair process and damage to the neural retinal represent additional sources of spectral sensitivity modulation that may explain some of the complexities of change observed in the post-exposure measurement period. These retinal sensitivity changes may provide a retinal basis for earlier behavioral investigations of punctate foveal damage where enhancement effects were observed.

Development of a test of foveal function during and after small spot foveal exposure was the primary objective of this investigation. This objective was accomplished. At retinal damage levels, only a small focal foveal lesion was observed indicating the ability to utilize the fovea during such exposure. Postexposure recovery effects analyzed for target size and contrast conditions suggest retinal and possibly cortical saturation processes.

Laser medical system safety is discussed. Several anecdotes are given to illustrate the need for safety logic circuits. Examples of possible failures and malfunctions are given. Safety logic specifications are discussed. The need to monitor the safety circuits is pointed out.