The acoustic boundary conditions at the site of laser irradiation affects the onset of cavitation when stress- confined laser pulses are used. This study reports the thresholds for cavitation when the laser pulse length exceeds the stress confinement time by a factor of eight. The cavitation threshold was defined as the loss of an acoustic signal from the collapse of the cavitation bubble in room temperature dye solutions. The threshold temperature increase for cavitation at a free surface was 13 plus or minus 3 degrees Celsius, at the tip of a 200 micrometer fiber in an aqueous solution was 17 plus or minus 2 degrees Celsius, and at the interface of two acoustically matched boundary materials was 80 plus or minus 20 degrees Celsius.

The use of pulsed laser energy to clear arteries obstructed by thrombus (blood clot) and plaque has emerged as a promising method for the treatment of cardiovascular diseases such as myocardial infarction and stroke. Current techniques for laser thrombolysis are limited because they cannot completely clear the clot in arteries, especially where a large volume clot is presented. Mural clot is a potent stimulus for reocclusion. We suggest that the combination of laser thrombolysis and localized intramural delivery of clot-dissolving drugs during the procedure may be a solution to this limitation. Ninety pulses of 30 - 70 mJ were delivered onto gelatin-based thrombus model with a flushing catheter. A solution of 1 micrometer fluorescent particles as a drug model was injected at a rate of 4 mL/min in coincidence with the laser delivery. The controls were performed by injecting drug after laser thrombolysis. We measured the penetration of the particles in gelatin and the sizes of the lumen and stained areas. The results of this study demonstrated the possibility of enhancing laser thrombolysis by delivering drugs into thrombus. It was found that the particles could be driven several hundred micron in gelatin, and the lumen areas would be increased up to 25% if the areas were dissolved by the drugs.

This paper presents studies of microsecond ablation phenomena that take place during laser thrombolysis. The main goals were to optimize laser parameters for efficient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate for maximum material removal. The minimum radiant exposures to achieve ablation at any wavelength were measured. The results suggest that most visible wavelengths were equally efficient at removing material at radiant exposures above threshold. Ablation was initiated at surface temperatures just above 100 degrees Celsius. A vapor bubble was formed during ablation. Less than 5% of the total pulse energy is coupled into the bubble energy. A large part of the delivered energy is unaccounted for and is likely released partly as acoustic transients from the vapor expansion and partly wasted as heat. The current laser and delivery systems may not be able to completely remove large clot burden that is sometimes encountered in heart attacks. However, laser thrombolysis may emerge as a favored treatment for strokes where the occlusion is generally smaller and rapid recanalization is of paramount importance. A final hypothesis is that laser thrombolysis should be done at radiant exposures close to threshold to minimize any damaging effects of the bubble dynamics on the vessel wall.

In response to recent demand for increased debulking of large diameter coronary vascular segments, a large eccentric catheter for excimer laser coronary angioplasty has been developed. The outer tip diameter is 2.0 mm and incorporates approximately 300 fibers of 50 micron diameter in a monorail- type percutaneous catheter. The basic function of the device is to ablate a coronary atherosclerotic lesion with 308 nm excimer laser pulses, while passing the tip of the catheter through the lesion. By employing multiple passes through the lesion, rotating the catheter 90 degrees after each pass, we expect to create luminal diameters close to 3 mm with this device. Design characteristics, in-vitro testing, and initial clinical experience is presented.

Cardiovascular disease is the chief cause of death in the western world. Lutetium texaphyrin (PCI-0123) is a pure, synthetic, aqueous-soluble macrocycle that localizes in both cancerous lesions and atheromatous plaque. The lutetium texaphyrin complex is a potent photosensitizer in vivo, where it is activated by tissue-penetrating far red light (720 - 760 nm). Patient diagnosis and treatment planning are possible with PCI-0123 fluorescence imaging. In this study the localization and selective eradication of atheromatous plaque using PCI-0123 and photoangioplasty are discussed.

De-endothelialization is the main stimulus of intimal hyperplasia following vascular injury. In this study we investigated the time course of re-endothelialization in balloon injured and photodynamic therapy (PDT) treated aortas of New Zealand white rabbits. Twenty rabbits underwent balloon denudation of the abdominal aorta and were then sacrificed in groups of 4 animals 0, 1, 2, 4 and 8 weeks later. Twenty more rabbits underwent similar balloon denudation and were treated immediately afterwards with photodynamic therapy using the photosensitizer metatetrahydroxy phenyl-chlorin and endovascular illumination with 652 nm light. PDT treated rabbits were also sacrificed in groups of 4 animals at the same time intervals. A further 4 rabbits were sacrificed without any treatment to act as normal controls. The vasculature was perfusion fixed at 100 mmHg with 10% formal saline. The abdominal aortas were retrieved and five sections were cut from each aorta at 1 cm intervals, embedded in wax, sectioned and stained for endothelial cells using the Avidin Biotin complex/horseradish peroxidase technique for use with the monoclonal primary antibody CD31 from the clone JC70. Endothelial covering was measured using a light microscope and Magiscan image analysis system. Normal arteries showed a near full (92.1% plus or minus 3.0, mean plus or minus SEM) endothelial covering. Endothelium was removed completely after both balloon injury and PDT. In balloon injury alone there was progressive endothelial regrowth with (54.1 plus or minus 7.2) covering at 8 weeks. In contrast, endothelial regrowth was retarded in the aortas treated with balloon injury and PDT, with only (7.1 plus or minus 2.9) of covering at 8 weeks. The slow pace of re-endothelialisation is consistent with greater production of intimal hyperplasia in PDT treated vessels.

Thermodilution-based cardiac output measurements are made using iced saline or blood heated by resistive heating as a dilutable indicator. Because near-infrared irradiation penetrates sufficiently deeply into blood, it can safely deposit up to six times the energy of a resistive heater, improving the accuracy of the measurements while continuously monitoring cardiac output. We have developed a prototype system using 980 nm diode lasers to irradiate blood through a diffuser. This system was tested using an optical blood phantom and was compared to iced-saline injection and resistive heating. Three flow estimates were made at each of 18 combinations of stroke rate, stroke volume, and systole/diastole ratios. Accuracy was determined by the quality of the fit between the estimated flows and the actual flow. Reproducibility was determined by the normalized standard deviation. Results: Measurements made by saline injection were the most accurate (R² equals 0.982) and reproducible (NSD equals 2.8%). Power limitations on the resistive heating to ensure a safe blood temperature limited its accuracy (R² equals 0.537) and reproducibility (NSD equals 18.1%). Laser-based heating showed reasonable accuracy and reproducibility (R² equals 0.950, NSD equals 7.8%). Laser heating thus represents a potentially more accurate alternative to saline injection for cardiac output measurement than does resistive heating.

A bipolar Nd-YAG laser (1.064 micrometer) handpiece was experimentally examined for a venous dissection without scissors and sutures and clinically introduced for the vein graft harvesting in coronary artery bypass grafting (CABG). Experimental study: One hundred and thirty-five segments of the mongrel dog veins were employed. Nd-YAG laser was irradiated on the vein held by the bipolar Nd-YAG handpiece at the power of 5, 9, 13, and 17 watts, and success defined as a complete vein citing without bleeding at the laser-applied sites were gained in all except three; 97.8% of success rate. Laser exposure time for cutting the vein decreased in order to an increase of the applied laser power, and the veins of bigger diameter needed more longer exposure time in the group of the same laser power. An average exposure time was 4.4 seconds for the veins of 1 mm diameter at 13 watts. In histological examination, a vascular lumen at the cutting site was diminished and covered with a degenerated vascular wall, and bleeding was not seen in all specimen. Clinical study: In 18 cases of CABG the bipolar Nd-YAG handpiece was applied to cut the branches of the great saphenous vein without scissors and sutures. Forty-two grafts harvested by this handpiece were used for aortocoronary bypass grating. All were survived and the angiographic examination demonstrated a 90% of graft patency at an average period of 3.5 years after the operation. Laser-induced morphological change such as aneurysmal formation or graft stenosis was not recognized.

A novel laser catheter design has been utilized to assist in the removal of chronically implanted pacing leads. The catheter, or 'laser sheath,' uses fiber optics to convey pulsed 308 nm light from a CVX-300 XeCl excimer laser to the distal tip of the catheter. As the catheter is threaded over an implanted pacing lead, into the patient's vasculature, lasing action can be used to cut through fibrotic adhesions that typically overgrow the lead, making lead removal difficult. In a randomized clinical trial, greater than 300 patients have been treated with the laser sheath, with no complications secondary to the use of the laser. Leads were totally removed in nearly all laser cases. Design features of the laser sheath that contribute to its clinical success are discussed.

Ventricular tachycardia (VT) is a rapid and life-threatening cardiac arrhythmia that most often occurs after healing of myocardial infarction. The same catheter techniques that use resistive endocardial heating to treat supraventricular tachycardias are less effective against post-infarction VT, in part because cure of the latter arrhythmia requires large volume, deep tissue coagulation. Greater risk may also be incurred when standard percutaneous methods are used to induce deep tissue heating, because excess endocardial damage can cause mural thrombi, and a large area of non-lethal endocardial injury may itself generate VT. To address these problems we have developed a unique optical fiber for direct intramyocardial photocoagulation which, when coupled to a diode laser (805 nm), can generate lesions up to 1 cm deep and wide without disruption of the endocardium. With further refinement this system may effectively and safely cure post- infarction VT.

Successful restoration of audition in revision stapedotomies involves precise identification and correction of the pathological condition without traumatizing the inner ear. Conventional surgical procedures often lead to unsatisfactory audition results and inner ear damages. In revision stapedotomy, the carbon-dioxide laser provides the ear surgeon with three important advantages over the conventional technique: (1) improved diagnostic and therapeutic precision, (2) better stabilization of the new prosthesis in the oval niche, and (3) reduction of inner ear trauma through non- contact atraumatic management. The surgical procedure of revision stapedotomies with the carbon dioxide laser is discussed, and case examples are used to illustrate the diversity of pathological conditions that can be treated by carbon-dioxide laser surgery. Our experience with revision carbon-dioxide laser stapedotomy suggests an improvement of postoperative audition compared to the conventional technique and demonstrates a significant elimination of sensorineural deafness. The carbon-dioxide laser enables the ear surgeon to precisely and reliably correct conduction deafness recurring after stapedotomy.

This study investigates guinea-pig and horse tympanic membranes, sheep dura and chicken eggshell membranes in terms of thickness, histology and tissue interaction with the carbon-dioxide and the erbium:YAG laser. Comparison with formalin-fixed human tympanic membranes as reference structure has provided a suitable model for further research in laser myringotomy. The horse tympanic membrane seems to meet our demands regarding the three parameters mentioned above.

Lasers suitable for myringotomy are the erbium:YAG laser (2940 nm) and the carbon-dioxide laser (10600 nm). The study examines the laser-tissue interaction with tympanic membranes of guinea-pigs, horses and formalin-fixed human tympanic membranes and the effects demonstrated by light-microscopy and scanning-electron-microscopy. The minimum energy densities for a perforation with the erbium:YAG laser in guinea-pig ear drums and formalin-fixed human tympanic membranes are 8 J/cm² and 16 J/cm² respectively. There are no thermic side effects. With the carbon-dioxide laser thermic side effects only occur with energy transmission via silver halide polycrystalline fiber. The minimum power density for perforation is 400 W/cm² (pulse duration 50 ms). With the microslad 719 micromanipulator (Sharplan, Israel, Tel Aviv), the minimum power densities for perforation of guinea-pig and horse eardrums and for formalin-fixed human tympanic membranes are 150 W/cm², 300 W/cm² and 600 W/cm² (pulse duration: 50 ms) respectively. The minimum power density to achieve a perforation with the SwiftLase^TM 757 scanner (Sharplan, Israel, Tel Aviv), is 250 W/cm² in guinea-pig eardrums (pulse duration: 100 ms). A prototype of a hand-held carbon-dioxide laser otoscope is suitable for performing laser myringotomies in formalin-fixed human tympanic membranes.

Variations based on bone growth and development make stress and fracture propagation differ greatly in pediatric skulls as compared to adult skulls. Differentiating the stress propagation between the pediatric and adult skulls can improve diagnostic prediction when presented with direct frontal impact on a pediatric skull, a fairly common occurrence in the clinical environment. Critical diagnostic information can be learned from an in depth study of stress propagation as a function of impact force at critical locations on the periorbital region of the human skull. The Division of Pediatric Otolaryngology at Albany Medical College and InterScience, Inc. are utilizing electronic speckle pattern interferometry detection (ESPI) and high resolution imaging to evaluate and compare stress propagation in pediatric and adult skulls. A dual detection ESPI system was developed which integrates a medium resolution (2/3') CCD capable of real-time image processing, with a high resolution, megapixel detector capable of limited real time acquisition and image processing in software. Options to allow for high speed detection include integrating a custom, high performance image intensifier with the megapixel detector leg to be used as a high speed gate. The dual optical layout will allow for continuous and pulsed ESPI evaluation of calibrated impacts at specific landmarks on the skull. The goal of this work is to produce a full quantitative analysis of the stress propagation in pediatric versus adult skulls for a better understanding of bone dynamics. The work presented below concentrates on the development of the dual detection ESPI system and initial results achieved with an adult cadaver skull.

One of us has developed an improved partial ossicular replacement prosthesis that is easier to implant and, based on pilot clinical measurements, results in better high-frequency hearing as compared to patients receiving one of the alternative prostheses. It is hypothesized that the primary reason for this is because of the relatively light weight (about 25 mg) and low compliance of the prosthesis, which could conceivably result in better high frequency vibrational characteristics. The purpose of our initial work was to develop an instrument suitable for objectively testing the vibrational characteristics of prostheses. We have developed a laser based device suitable for measuring the vibrational characteristics of the oval window or other structures of the middle ear. We have tested this device using a piezoelectric transducer excited at audio frequencies, as well as on the oval window in human temporal bones harvested from cadavers. The results illustrate that it is possible to non-invasively monitor the vibrational characteristics of anatomic structures with a very inexpensive photonic device.

The acute and chronic (10 week) histological effects of the holmium:YAG laser during partial meniscectomy in an in vivo rabbit model were investigated. Twenty-four adult male New Zealand rabbits underwent bilateral parapatellar medial knee arthrotomies. In the right knee, a partial medial meniscectomy was done through the avascular zone using a standard surgical blade. In the left knee, an anatomically similar partial medial meniscectomy was performed using a Ho:YAG laser (Coherent, USA). This study indicates that the laser creates two zones of damage in the meniscal fibrocartilage and that the zone of thermal change may act as a barrier to healing. The zone of thermal change which is eventually debrided was thought at the time of surgery to be viable. In the laser cut menisci, the synovium appears to have greater inflammation early and to be equivalent with the scalpel cut after three weeks. At all time periods there appeared more cellular damage in the laser specimens.

Laser treatment of skin changes has become common practice in recent years. The high absorption of the wavelength of the carbon-dioxide laser (10600 nm) is responsible for its low penetration depth in biological tissue. Shortening the exposure time minimizes thermic side effects such as carbonization and coagulation. This effect can be achieved with the SilkTouch^TM scanner 767, since the focused laser beam is moved over a defined area by rapidly rotating mirrors. This enables controlled and reliable removal of certain dermal lesions, particularly hypertrophic scars, scars after common acne, wrinkles, rhinophyma and benign neoplasms like verruca vulgaris. Cosmetically favorable reepithelialization of the lasered surfaces results within a very short period of time. Benign mucosal changes of the upper aerodigestive tract can also be treated. Ablation is less traumatic for papillomas, fibromas, hyperplasias in the area of Waldeyer's tonsillar ring and certain laryngotracheal pathologies. Clinical examples demonstrate the advantages of this new mode of application.

In order to better understand the interaction of laser light with biological tissue, a light-transport model is integrated with a heat-transport model. The outputs include temperature as a function of position and time, given the illumination conditions and the optical and thermal properties of the tissue. The optical portion of the algorithm is based on the theory of radiative transfer through a turbid medium. Our computer program models multiple scattering in three dimensions using seven discrete irradiances which approximate the radiative transport equation. The distribution of absorbed light in the tissue is calculated and used as the source term in a discrete approximation to the thermal diffusion equation. Recently, we have been using the model to better understand the laser-heating of heterogeneous tissue. Rather than modeling a homogeneous mixture having properties given by weighted averages of those of tissue and blood, we model this medium as an array of blood vessels in a bloodless dermis background. We are currently analyzing temporal and spatial variations of temperature in homogeneous and heterogeneous tissue having identical blood concentrations. A particular application of the model is to the study of laser coagulation tonsillectomy.

We have tested a combined treatment for squamous cell carcinoma based on laser activation of anti-cancer drugs in human solid tumors. Cisplatinum and the new anthrapyrazole CI- 941 are reported to interact with photothermal energy. Combined intratumor drug and interstitial laser therapy were tested in nude mice bearing human squamous cell carcinomas grown as subcutaneous tumors. Cisplatinum injection (1.2 mg/500 mg tumor) 4 hours before KTP laser fiberoptic treatment (532 nm, 0.8 W, 10 sec/site, 300 J) resulted in complete tumor regression in 6/8 animals, while intratumor drug alone led to partial regression and tumor regrowth in 10/10 mice during 12 weeks followup. Laser treatment alone resulted in ablation followed by recurrence in 7/8 cases. Similar laser treatment 4 hours after injection of the light sensitive anthrapyrazole CI-941 led to complete tumor regression in 15/22 cases. CI-941 alone at drug levels up to 1.2 mg/gm tumor in 30 mice induced stasis followed by progression in all cases. Finally, tumor retention of ¹⁴C-CI-941 in mice 4 hrs after intralesional injection was 200-fold higher than via the systemic route and by 24 hrs remained 40-fold higher, but drug levels in normal tissues were reduced 10 - 100 fold. The data suggest laser chemotherapy may be a useful new treatment for human cancer.

For laser safety it is absolutely necessary that endotracheal tubes do not ignite under exposure of laser radiation. Furthermore these tubes should remain in working condition. A critical point was observed in the conduits which are used to expand the cuffs at the distal end of the tube. In some constructions these conduits are guided in the inner lumen of the tube. It was seen experimentally that laser exposure can destroy the conduits which leads to a narrowing of the gas flow through the tube. The gas flow resistance inside of different tubes was measured while the tubes were exposed by carbon-dioxide laser radiation. Caused by the specific constructions and the physical properties of the materials, the flow resistance of some tubes changed, while it was constant in other tubes. These experimental results were compared with results observed during the clinical use of different tubes.

Pulsed IR and UV lasers have been suggested for use in middle ear surgery due to decreased thermal trauma, precise ablation characteristics, and potential fiberoptic delivery. While there has been much focus on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies that look at the acoustic energy generated from these devices from an audiologic standpoint. In this study, the mastoid cavities of cadaveric human temporal bones were irradiated with a Ho:YAG laser (lambda equals 2.12 micrometer) with the following parameters: 5, 10, and 15 Hz pulse repetition rate and 1, 2, 4, 6, 8, and 10 W average power. During ablation, acoustic measurements were made using a sound level meter held 5 cm away from the target site. With each set of laser parameters, the sound intensity (dB SPL) exceeded 85 dB. Peak intensity measurements of 125 dB were measured, and a saturation effect was noted above 4 W or 500 mJ/pulse. The clinical significance of these findings is discussed and the acoustical aspects of middle ear function and noise trauma are reviewed.

Laser Doppler vibrometry is a well established technique to measure tiny motions without mechanical contact. Therefore this technique is suitable to detect the motions of the human hearing organ. For the clinical application of laser Doppler vibrometry different optical setups were used for the delivery system. The laser beam was guided by an optical fiber using the commercial output optic or a micro probe which had such a small diameter that it could be brought into the outer ear canal. The large number of successful measurements showed that laser Doppler vibrometry can be used in clinical routine. While the reproducibility of the method was seen to be sufficient, the variation from one person to another is seen as a critical point to apply this method for clinical diagnosis. The presentation focuses on the technical possibilities and limitations to improve the setup for a better clinical application.

Transendoscopic application of Nd:YAG laser energy for treatment of partial upper respiratory obstruction in the horse has been practiced for the last 12 years in both contact and non-contact modes. Endoscopic laser ablation has been limited to wavelengths transmitted through flexible optical fibers. Devices used for this purpose have been primarily the Nd:YAG (1064 nm), KTP (532 nm), holmium (2100 nm), and diode (805 nm) lasers. Few investigations have focused on use of the holmium or diode lasers. Objectives of this study were to evaluate use of fiber-deliverable laser wavelengths provided by newer, more portable, user-friendly, solid-state diode and holmium lasers for ablation of laryngeal tissues of the equine upper respiratory tract. In addition, information on efficacy and dosimetry for both the contact and non-contact modes was obtained using an in vitro cadaveric model. Preliminary conclusions based on histologic evaluation and scanning electron microscopy revealed that diode laser energy has the ability to penetrate laryngeal tissue easily and deeply with minimal collateral coagulation, but is sensitive to tissue color. Holmium laser energy can be used to incise laryngeal tissue easily in contact mode with moderate collateral damage, and absorption does not seem dependent on tissue color.

Hospital medical surgery records and laser logs were examined to determine the population of large animals presented to the College of Veterinary Medicine treated by laser and conventional means for cystic lesions. Cystic lesions were most frequently found in 2 anatomical locations: endometrial cysts and upper respiratory cysts. The majority of endometrial cysts were considered to be acquired, whereas the most frequently encountered upper respiratory cysts were believed to be congenital due to the fact they were most frequently seen in young animals. Nine mares, totaling 42 endometrial cysts, were presented to the Veterinary Teaching Hospital (VTH), all of which had been treated by transendoscopic Nd:YAG laser ablation. Eighteen of the respiratory cysts in the same time period were presented to the VTH, of which 10 received conventional surgery and 8 were laser photoablated. Respiratory cysts treated by conventional surgery were generally found in locations inaccessible to visualization by transendoscopic technique, and thus required a surgical approach under general anesthesia. All mares with endometrial cysts were presented with a history of conception failure. After laser ablation, a majority of the mares were able to carry a foal to term and none represented with recurrence of endometrial cysts. Horses that presented with upper respiratory cysts also did not experience recurrence of cysts; although several horses, 1 treated by laser ablation and 4 treated by conventional surgery for frontal and/or maxillary sinus cysts, had transitory sinusitis. Transendoscopic Nd:YAG photoablation of cysts appears to be a very satisfactory means of treating this particular form of lesion in large animals with minimal complications and it can be performed with the animal in a standing position as an outpatient.

The objective of this study was to evaluate carbon-dioxide laser surgical treatment of pulpal exposures in canine patients. Seventeen permanent teeth with exposures of less than or equal to 48 h were randomly allocated to receive either (1) localized laser pulp surgery to remove all compromised soft tissues or (2) localized pulp surgery using a large round sterile bur under sterile saline irrigation. Single laser pulses were used at 0.01 s pulse duration, 1.0 s pulse interval, a spot size of 0.004 cm² and an energy density of 276 J/cm². Exposures were dressed with CaOH and glass ionomer. Clinical and radiographic evaluations were performed by one blinded clinician 4, 12, 24 and 52 weeks after treatment using standard scales of 0-(-1). Fifteen/seventeen laser-treated teeth assessed over greater than or equal to 1 year post-treatment remained clinically and radiographically healthy.

Urolithiasis is a common disease affecting dogs which can sometimes be treated with dietary and medical protocols. In many cases, however, medical management cannot be employed because the dietary restrictions are contraindicated, effective medical dissolution protocols for the calculi (uroliths) do not exist, or obstruction by the calculi may result in deterioration of renal function during the time required for medical dissolution. At present, the management of medically untreatable calculi has been surgical removal which may result in temporary but dramatic decrease in renal function, irreversible loss of damaged nephrons, and significant risk, particularly for bilateral or recurrent nephroliths. An innovative technique for the removal of these uroliths would involve laser lithotripsy which transforms light energy into acoustical energy generating a shock wave sufficient to fragment stones (photoacoustic ablation). The laser is transmitted via quartz fibers which are small and flexible and can be used under direct vision through endoscopes resulting in effective fragmentation with little surrounding tissue damage. Lasers are becoming increasingly more utilized in veterinary medicine, in contrast to the limited availability of other non-invasive methods of treatment of nephroliths (i.e. extracorporeal shock-wave lithotripsy).

The ability of low-energy laser radiation (LLR) to counteract the detrimental effects of gamma radiation was studied with a murine model. Three control and two experimental groups of mice were used. Control group I consisted of animals unexposed to either gamma or laser irradiation. Group II consisted of mice exposed solely to gamma radiation. Control group III consisted of mice exposed solely to LLR. Experimental group I included mice exposed to gamma radiation initially, followed by LLR for three days. In experimental group II, LLR was applied each of three days prior to gamma irradiation. Gamma radiation was produced by 137 Cs with a total dose of 8.75 Gr (0.02 Gr/min). The source of laser radiation was He-Ne (632.8 nm), and a power density of 0.5 Wt/cm². Irradiation was performed once every three days for 15 sec. In an additional set of experiments, the effect of LLR in various doses on survival of gamma-irradiated mice was examined. The effects of laser exposure prior to and after gamma radiation, percent survival, changes in lipid peroxidation in serum and liver, the concentration of S-H groups in serum, and catalase activity in erythrocytes were obtained. LLR reduced average lethality. Successful results were achieved in all sets of experiments and were dependent mostly on the dose of LLR. The biochemical tests exhibited the ability of LLR to modify the damaging effects of gamma radiation when laser is applied prior to or after gamma radiation. However, the protective effect of LLR was greater in the group with exposure before gamma radiation.

Laser welding with albumin-based tissue solder has been investigated as an alternative to surgical suturing. Many surgical procedures require the soldered tissues to be in a hydrated environment. We have studied the effects of hydration on laser soldered rat dermis and baboon articular cartilage in vitro. The solder is composed of human serum albumin, sodium hyaluronate and indocyanine green. We used a micro-pipette to deposit 2 (mu) l of solder on each tissue specimen. An 808 nm cw laser beam with irradiance of 27 W/cm² was scanned 4 times over the same solder area at a constant speed of 0.84 mm/sec. After photo-coagulation, each tissue specimen was cut into two halves at the center of the solder, perpendicular to the direction of the scanning laser beam. One half was reserved as control while the other half was soaked in phosphate buffered saline for a designated hydration period. The hydration periods were 1 hr, 1, 2, and 7 days. All tissue specimens were fixed in glutaraldahyde, then prepared for scanning electron microcopy analysis. For most of the specimens, there was non-uniform coagulation across the thickness of the solder. Closer to the laser beam, the upper solder region formed a more dense coagulum. While the region closer to solder-tissue interface, the solder aggregated into small globules. This non-uniform coagulation was likely caused by non-uniform energy distribution during photocoagulation. The protein globules and coagulum seem to be responsible for the solder attachment from the specimen surface. However, we have noted that the solder detached from the cartilage substrate as early as after 1 hr of hydration. On the other hand, the solder attached to the dermis much better than to cartilage. This may be explained by the difference in surface roughness of the two tissue types. The dermal layer of the skin is composed of collagen matrix which may provide a better entrapment of the solder than the smooth surface of articular cartilage.

An in vivo study of vascular welding with a fiber-delivered argon laser was conducted using a canine model. Longitudinal arteriotomies and venotomies were treated on femoral vein and artery. Laser energy was delivered to the vessel wall via a 400 micrometer optical fiber. The surface temperature at the center of the laser spot was monitored in real time using a hollow glass optical fiber-based two-color infrared thermometer. The surface temperature was limited by either a room-temperature saline drip or direct feedback control of the laser using a mechanical shutter to alternately pass and block the laser. Acute patency was evaluated either visually (leak/no leak) or by in vivo burst pressure measurements. Biochemical assays were performed to investigate the possible laser-induced formation or destruction of enzymatically mediated covalent crosslinks between collagen molecules. Viable welds were created both with and without the use of feedback control. Tissues maintained at 50 degrees Celsius using feedback control had an elevated crosslink count compared to controls, while those irradiated without feedback control experienced a decrease. Differences between the volumetric heating associated with open and closed loop protocols may account for the different effects on collagen crosslinks. Covalent mechanisms may play a role in argon laser vascular fusion.

Meniscal tears and partial thickness defects in articular cartilage do not heal spontaneously. In this paper results are described of studies of a procedure for evoking the healing response in such lesions by a non-thermal tissue sparing photochemical weld using 1,8-naphthalimide dyes. Fifteen essentially mature Barbados sheep 40 - 60 pounds in weight received a 2 - 3 mm flap tear by incision in the red white zone of the medial meniscus oriented parallel to the table of the tibia. The animals were divided into four groups; Group I, no treatment; Group II, treatment by laser activated photoactive dyes; Group III, treatment by suturing; Group IV, treatment by laser irradiation only; Group V, treatment by photoactive dyes only. In another group of 12 sheep partial thickness flap tear was created by incision in the articular cartilage of the femoral condyle. These were divided into four groups as for the meniscus study, omitting the sutured control. Welds were made using the dimeric dye MBM Gold BW 012-012-012 at 12 mM in PBS, 457.9 nm argon ion laser radiation at 800 mW/cm², 7.5 minutes (360 J/cm²) with approximately 2 kg/cm² externally applied pressure. Animals were sacrificed at 24 hr, 4 weeks, 3 and 6 months postoperatively. Gross appearance of menisci and cartilage in all welded knees was normal and all welds resisted deformation or loosening under forceful probing. Histology of studies of both tissues out to 6 moths disclosed close bonding of welded area, continuing healing response in the form of cellular recruitment and protein deposition and the absence of inflammatory response. Tissue erosion and arthritic changes were evident in all unwelded controls.

The strength and stability of laser-welded tissue may be influenced, in part, by the effects of laser exposure on collagen crosslinking. We therefore studied the effects of diode laser exposure (805 nm, 1 - 8 watts, 30 seconds) plus indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. The effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p less than 0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relationships are maintained. We conclude that: (1) ICG alone induces DHLNL and OHP crosslink formation; (2) subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3) excessive diode laser exposure destroys normally occurring HLNL crosslinks.

We performed imaging and reconstruction of dermal and subdermal blood vessels in a rat skin flap window model. The window model consists of a double thickness of dorsal skin which is sutured to a holding fixture. A 1 cm circle of skin is removed from one thickness, exposing the dermal blood vessels of the opposing side. An optical coherence tomography system operating at 1310 nm was used to image the blood vessels. A series of transverse images of the window model characterized sections of tissue. Off-the-shelf software for desktop and workstation computers was used to preprocess the images, identify and reconstruct blood vessels, and to extract parameters such depth, diameter, and percent volume of blood vessels. Such parameters may be of interest in developing improved treatments for vascular disorders such as port wine stains.

Opto-thermal in-vivo measurements of stratum corneum hydration can now be evaluated to give hydration depth profiles from a mathematical model that incorporates both the surface hydration and the changes of hydration with depth beneath the surface. We now present an analysis of water diffusion in the stratum corneum that can be related to such measurements. The results are compared with measurements of changes of surface hydration and hydration gradient with depth in a stratum corneum stripping experiment. Surface hydration and hydration gradient information can also be combined to yield a measure of stratum corneum thickness, as illustrated with a measured thickness map of the volar forearm.

Pulsed carbon-dioxide laser skin resurfacing is a purportedly 'non-thermal' procedure enjoying wide application as a cosmetic treatment for skin wrinkles. Treatment success has been based on clinical assessments of skin smoothness. Skin lesions (1 cm²) created by one, two or three superimposed carbon-dioxide laser passes were placed on the backs of 28 'fuzzy' Harlan Sprague Dawley rats. The variable laser irradiation parameters included measured energies ranging from 112 to 387/pulse with pulse widths of 65 and 125 microseconds and a repetition rate of 8 Hz. The square, flat laser beam measured 3 mm² at the focal point. The lesions were collected from 0 to 10 days after treatment for qualitative and quantitative histopathology. Thermal damage and treatment effect tended to increase in severity and, to a lesser extent, depth with increased delivery parameters. In acute lesions, the vacuolated and fragmented, desiccated and thermally coagulated epidermis was partially removed exposing the underlying thermally coagulated dermal collagen and cells. Epidermal and dermal necrosis and slough occurred between 24 to 72 hours after treatment. Epithelial regeneration originated from the adnexa and the lesion edges. Dermal fibrous scar formation began at 5 days below the regenerated epidermis and became more prominent at 7 and 10 days.

An increasing number of lasers are in clinical use for treatment of facial rhytides and scars. Each one of these lasers has a significantly different delivery profile while sharing a photothermal mechanism to ablate surface layers of skin. The biological mechanism by which smoother skin results is still under study. Factors in achieving clinical improvement may include tissue ablation, tissue shrinkage, and the inflammatory response produced by the layer of thermally injured dermis which underlies the ablated skin or produced by the need to heal a large raw skin surface. Clinical results suggest that the available lasers all produce some measure of the 'resurfacing effect.' Given the diversity of delivery parameters employed, a comparison of the tissue effects would be useful. We sought to compare the depth of thermal injury and the degree of tissue shrinkage produced by three commonly used resurfacing lasers.

Optical low coherence tomography (OCT) is a newly developed bioengineering method for noninvasive in-vivo investigation of human skin, especially of the epidermis. Based on the principle of a Michelson interferometer, OCT allows the detection of the path length of an infrared light beam after backscattered inside the skin sample by comparison with a reference beam. The depth resolution is limited by the coherence length of the light source, which is about 15 micrometer. OCT supplies cross-sectional images of the skin with a penetration depth of about 0.5 to 1.5 mm. The stratum corneum can be distinguished from the living epidermis and the upper dermis. We investigated healthy skin of several localizations, inflammatory diseases, intra- and subepidermal blisters and epidermal tumors. First images are presented to demonstrate the possibilities of this promising new method.

We measured the acute tissue shrinkage using a continuous wave and a pulsed carbon dioxide laser for skin resurfacing. The tissue shrinkage was measured on in vitro, non-facial human skin samples. We also examined the amount of thermal damage in the skin acutely and three days after laser resurfacing using a piglet model. The pulsed laser used a 100 microsecond pulse and delivered 500 mJ in a 3 by 3 mm square spot. The continuous wave laser was delivered with a hand piece that moved the beam in a 3.4 mm spiral during the 0.2 s irradiation. The continuous wave laser was set to 8 W. As expected, the pulsed laser showed less thermal damage acutely and after three days when compared to the continuous wave laser. However, the pulsed laser also showed more tissue shrinkage than was observed with the continuous wave laser. These results imply that the tissue shrinkage from carbon dioxide laser resurfacing may be related to the tissue removal more than collagen denaturation.

The thermal consequences of a 100 microsecond carbon-dioxide laser used for skin resurfacing were examined with infrared radiometry. Human skin was evaluated in a cosmetic surgery clinic and extirpated rodent skin was measured in a research laboratory. Thermal relaxation following single pulses of in vivo human and ex vivo animal skin were quantitatively similar in the 30 - 1000 msec range. The thermal emission from the area of the irradiated tissue increased monotonically with increasing incident laser fluence. Extremely high peak temperatures during the 100 microsecond pulse are attributed to plume incandescence. Ejecta thermal emission may also contribute to our measurements during the first several msecs. The data are combined into a thermal relaxation model. Given known coefficients, and adjusting tissue absorption to reflect a 50% water content, and thermal conductivity of 2.3 times that of water, the measured (both animal back and human forearm) and calculated values coincide. The high thermal conductance suggests preferential thermal conduction along the protein matrix. The clinical observation of a resurfacing procedure clearly shows thermal overlap and build-up is a result of sequential, adjacent pulses. A decrease of 4 - 6 degrees Celsius in surface temperature at the treatment site that appeared immediately post-Tx and gradually diminished over several days is possibly a sign of dermal convective and/or evaporative cooling.

The application of pulsed carbon-dioxide lasers for skin resurfacing has been described by several authors. The procedure uses 30 microseconds to 1 ms laser pulses with pulse energies from 100 - 600 mJ to ablate skin for the purpose of smoothing skin irregularities: that is, wrinkle removal. The carbon-dioxide laser has been selected because it ablates a limited layer of tissue (approximately 10 micrometer at a radiant exposure of 5 J/cm²)⁴ and produce minimal thermal damage. The purpose of this study is to measure the surface temperature created during a resurfacing procedure and discuss the thermal implications of the measurements.

Currently the most commonly accepted treatment for port wine stains (PWS) is the process of selective photothermolysis using pulsed lasers. In principle light is absorbed by the blood heating the vessel walls leading to subsequent destruction. The wavelength should be chosen so that the light is absorbed well by haemoglobin, but not by the skin tissue. There is evidence to suggest that the pulse length should be chosen to match the thermal relaxation time of the blood vessels. For individual vessels this is around 10 ms or below. If we consider the whole PWS there are indications that pulse lengths greater than this may be more suitable and a range of pulse lengths may be required. Varying the pulse length with a laser can be difficult. With the development of intense white light sources, variations in wavelength, pulse width and fluence can be achieved and therefore allow versatility in selective photothermolysis treatment. The development of a prototype intense, filtered, white light source to treat PWS has been undertaken. A short-arc, Xenon filled lamp has been incorporated into a system whereby it is possible to have a modulated output of varying pulse-lengths (approximately 30 ms - 400 ms) and energies of 0.5 J - 2 J. The filtered (525 nm - 625 nm) light is delivered through a liquid light guide giving a spot size of 5 mm. This prototype has been developed, is being evaluated clinically, and could have the potential to treat a wide variety of vascular lesions (especially dense PWS) and yet be small, robust and inexpensive. A summary of the development, performance and initial trials is presented.

A selective photothermolysis model has been widely used to explain skin tissue ablation by nanosecond laser pulses. Nevertheless, fundamental questions regarding the mechanism underlying the ablation process remain to be answered. We have investigated the surface ablation of fresh porcine skin tissue with 8 ns pulses at 1064 nm and its dependence on spot size. Histology analysis of the ablated tissue samples has been conducted. From these preliminary results we have plotted the ablation depth per pulse as a function of laser fluence at different spot sizes.

The purpose of this study is to evaluate the safety and effectiveness of the New Star Model 130 neodymium:yttrium aluminum garnet (Nd:YAG) laser system for nonablative laser treatment of facial rhytides (e.g., periorbital wrinkles). Facial rhytides are treated with 1.32 micrometer wavelength laser light delivered through a fiberoptic handpiece into a 5 mm diameter spot using three 300 microsecond duration pulses at 100 Hz pulse repetition frequency and pulse radiant exposures extending up to 12 J/cm². Dynamic cooling is used to cool the epidermis selectively prior to laser treatment; animal histology experiments confirm that dynamic cooling combined with nonablative laser heating protects the epidermis and selectively injures the dermis. In the human clinical study, immediately post-treatment, treated sites exhibit mild erythema and, in a few cases, edema or small blisters. There are no long-term complications such as marked dyspigmentation and persistent erythema that are commonly observed following ablative laser skin resurfacing. Preliminary results indicate that the severity of facial rhytides has been reduced, but long-term follow-up examinations are needed to quantify the reduction. The mechanism of action of this nonablative laser treatment modality may involve dermal wound healing that leads to long- term synthesis of new collagen and extracellular matrix material.

Lower eyelid skin is very thin with a low density of adnexal structures. Attempts to remove rhytides and improve surface appearance with chemical peels and dermabrasion have been disappointing. Laser resurfacing offers a new modality that may improve the outcome. We evaluated a very short duration (100 microsecond(s) ec) pulsed carbon-dioxide laser (Tru-Pulse^TM) in terms of healing time (duration of erythema) and efficacy (wrinkle reduction). Female patients aged 35 - 75 received laser resurfacing in a variety of cosmetic zones but only data from lower lids are reported here. Dosimetry varied from total fluences of 5 to 20 J/cm² (9 mm² spot, 250 - 500 mJ pulse, 1 to 4 passes). Patients followed a strict regime of post-op wound care. Pre-treatment and follow-up photographs were taken in a studio with constant photographic parameters. Projected 35 mm slides were evaluated side-by-side for clinical improvement and presence of erythema. Within the first 4 days post-op all (100%) lower eyelids exhibited erythema and swelling, at 7 days: 71%, 12 days: 60%, 3 weeks: 25%, and one (1) month or longer 7%. In our sample the longest duration of post-op lower lid erythema lasted 5 weeks. Most patients experienced 70 -80% wrinkle reduction with a range of 0 - 100%. Regression analysis was used to evaluate the relationships between percent wrinkle reduction and the treatment, demographic, and evaluation variables. There was a significant trend for wrinkles to improve over the 3 to 9 month evaluation period. Older patients improved slightly more than younger patients. There was no relationship between total energy density and wrinkle reduction.

Nonablative skin resurfacing is a dermatologic procedure utilizing pulsed laser irradiation and dynamic cooling to induce selectively a wound healing response in the papillary and upper reticular dermis. Using temperature measurements of human skin provided by pulsed photothermal radiometry immediately following laser irradiation (lambda equals 1.32 micrometer), spatial distribution of thermal damage is predicted in response to various potential therapeutic laser- cryogen doses. Results of our analysis suggest that appropriate application of pulsed laser irradiation and cryogen spray cooling may be used to protect the epidermis and selectively confine thermal injury to the papillary and upper reticular dermis. Development of nonablative skin resurfacing will require understanding the relationship between the degree of dermal photocoagulation and the cutaneous wound healing response following laser irradiation.

It has been shown that laser ablation of stratum corneum, in vitro, can result in an increased uptake of topically applied pharmaceuticals. We have performed measurements of drug permeation, using an in vitro model of human skin, that involves a portable Er:YAG laser used to ablate the stratum corneum. For the first time, this method of drug administration was tested in vivo in human volunteers, whereby a hydrocortisone blanching assay was used to assess the efficiency of the procedure. The results show that this is a safe and efficient way to ablate stratum corneum for the purpose of enhanced transcutaneous drug administration.

Cartilage undergoes characteristic deformation following laser irradiation below the ablation threshold. Measurements of surface temperature and integrated scattered light intensity were performed during laser irradiation. Porcine auricular cartilage (1 - 2 mm thickness) was irradiated with an Nd:YAG laser (lambda equals 1.32 micrometer) with varying dose (J/cm²). Surface temperature was monitored using a single element HgCdTe infrared detector, responsive between 10 - 14 micrometer. A HeNe laser beam (lambda equals 632.8 nm) was incident on the back surface of the cartilage specimen and fractional integrated back scattered light intensity was measured using an integrating sphere and a silicon photodiode. Laser irradiation (2 W, 5.83 W/cm², 50 Hz PRR) was allowed to proceed until surface temperature reached 70 degrees Celsius. Cartilage deformation was observed in each instance. Integrated scattered light intensity reached a plateau before the peak temperature (70 degrees) was reached. At increased laser power (10 W, 39.45 W/cm², 50 Hz PRR), a feedback controlled cryogen spray was used to maintain surface temperature below 50 degrees Celsius. A similar plateau response was also noted in integrated scattered light intensity. This signal may be used to optimize the process of stress relaxation in laser cartilage reshaping. Several clinical applications are discussed.

Determination of optimal treatment parameters and appropriate methods of examination for Nd:YAG laser coagulation of the human prostate in dependence of power-setting and time using the SideFocus^R side-firing delivery system. Transurethral free-beam laser coagulation was performed in 10 patients prior to planned radical prostatectomy. Thereof 6 underwent laparoscopic lymphadenectomy and laser coagulation of the prostate between 4 and 9 days prior to open surgery. These same patients had undergone MRI-examination with an endorectal coil during staging and prior to radical prostatectomy. Depth and volume of coagulated prostatic tissue of a 4-quadrant laser application were measured at power settings of 40 W/90 s and 60 W/60 s. There was no difference in volume coagulation between the two treatment modalities. In contrast there was a significant difference in volume coagulation between those prostates removed at 4 to 9 days and those removed t 60 to 210 minutes after laser coagulation. In histological and MRI- examination, however, there was a strong correlation with view to coagulation volume. Both treatment modalities showed comparable volume coagulation with laser induced changes conclusively discernible by 4 days. MRI-examination with an endorectal coil proved to be perfectly suitable for assessment.

A randomized, double blind, power determined, prospective study compared patients with benign prostatic hyperplasia undergoing endoscopic laser ablation of prostate, ELAP, -- Group 1 -- to those with KTP bladder neck incision and ELAP -- Group 2. A dual wavelength Laserscope KPT/532TM laser was used with add/stat side-firing fibers. Post-operatively a urethral catheter was inserted, which was removed at 18 hours. Patients unable to void at this stage where then re-catheterized, discharged and readmitted two weeks later for catheter removal. Patients were followed up at three month intervals. Eighty eight patients were studied, pre-operatively there was no statistical difference between Group 1 and Group 2 in mean age, 68.0, 68.4 yrs; prostate size 28, 29 g; post void residual, PVR, 141, 126 ml; max flow rate, Qmax, 9.8, 9.4 ml/s; or AUA score 18.0, 20.4; respectively. Post-operatively 57% of Group 1 patients were able to void on catheter removal at 18 hours compared to 80% from Group 2; p less than 0.05, (chi) ². After one month, two patients from Group 2 and one from Group 1 failed to void and required further surgery. At six months, data for Group 1 and 2 respectively: PVR equals 78.7, 61.4 ml, Qmax equals 16.2, 18.1 ml/s, AUA score equals 9.6, 6.38, p less than 0.005 for each. Group 2 had a significantly greater improvement in AUA7 score than Group 1.

The objective of this study was to evaluate and compare the safety and efficacy of the KTP 532 laser to direct vision internal urethrotomy (DVIU) in the management of urethral strictures. A total of 32 patients were randomized prospectively in this study, 14 DVIU and 18 KTP 532 laser. Patients were evaluated postoperatively with flowmetry and in the case of recurrence with cystourethrography at 3, 12, 24 weeks. With the KTP 532 laser complete symptomatic and urodynamic success was achieved in 15 (83%) patients at 12 and 24 weeks. Success rate was lower in the DVIU group with 9 (64%) patients at 12 weeks and 8 (57%) patients at 24 weeks. With the KTP mean preoperative peak-flow was improved from 6 cc/s to 20 cc/s at 3, 12 and 24 weeks. With DVIU mean preoperative peak-flow was improved from 5.5 cc/s to 20 cc/s at 3 weeks followed by a steady decrease to 13 cc/s at 12 weeks and to 12 cc/s 24 weeks. No complications were observed in either group of patients. Our results confirm that stricture vaporization with the KTP 532 laser is a safe and efficient procedure. It thus represents a valuable alternative in the endoscopic treatment of urethral strictures.

The holmium laser is becoming an important tool in the urologists' armamentarium. In this manuscript the evolution of laser resection of the prostate using the holmium wavelength is described. This technique represents a significant advance in the surgical management of benign prostatic hyperplasia and allows even very large prostates to be safely and efficiently managed transurethrally.

The purpose of this study is to report early complications in our initial experience with the holmium laser in 133 patients. A retrospective study of patients undergoing endourological procedures with the holmium laser was performed. Complications included urinary tract infection (3), post-operative bradycardia (1), inverted T-waves (1), intractable flank pain (1), urinary retention (1), inability to access a lower pole calyx with a 365 micron fiber (9), stone migration (5), termination of procedure due to poor visualization (2). No ureteral perforations or strictures occurred. The holmium laser was capable of fragmenting all urinary calculi in this study. In our initial experience, the holmium laser is safe and effective in the treatment of genitourinary pathology. Use of laser fibers larger than 200 microns occasionally limit deflection into a lower pole or dependent calyx.

We performed a pilot evaluation of the 200 micron holmium laser fiber to treat a variety of ureteral and renal calculi. The 200 micron laser fiber has the potential advantage of being more malleable and therefore having increased deflectability compared to larger laser fibers. A total of sixty patients underwent treatment for urinary calculi either primarily or as an adjunct. Thirty-three intrarenal stones and 26 ureteral stones were ureteroscopically treated with the 200 micron holmium laser fiber. Mean stone burden was 12.8 mm for renal stones (range equals 3 - 40 mm) and 7.7 mm for ureteral stones (range 5 - 15 mm). The ability to treat calculi in dependent calices and energy required to fragment calculi were studied. In addition, a bench top study was performed to determine the effect of the 200 micron fiber on active deflection of various flexible ureteroscopes. The bench studies revealed that the 200 micron fiber limited the flexibility of the ureteroscopes from 9 to 43 degrees depending on the ureteroscope. In spite of the limitation demonstrated in the bench top studies, in vivo we found that using the small diameter laser fiber, we could access and treat calculi located within dependent and lower pole calices. In addition, although the 200 micron fiber did inhibit deflection of flexible ureteroscopes, in all cases we were able to obtain access to the lower pole using this fiber.

Transurethral microwave thermotherapy (TUMT) has been widely reported for the treatment of benign prostatic hyperplasia (BPH) but with variable results. This is likely due to the inability to develop and maintain high intraprostatic temperatures. The T3 device has a preferential heating pattern which prevents shutdowns as a result of rectal heating thus allowing continuous energy delivery throughout the therapy. High temperatures greater than 70 degrees Celsius are maintained resulting in extensive coagulative necrosis in the transitional zone. Treatment was performed in an outpatient clinic using topical anaesthesia with occasional low dose I.V. analgesia. One hundred and fifty-four patients have been treated in 3 centers using a similar protocol. Inclusion criteria required an AUA symptom score greater than or equal to 9 and a peak uroflow rate less than or equal to 12 ml/sec. Mean prostate size was 40.6 cc. One hundred and eighteen patients have been followed for at least 12 months, and 58 for 24 months. AUA symptom score decreased from a mean of 19.8 to 8.9 (12 M), and 7.6 (24 M). Improvement was seen in all 7 symptoms evaluated. Peak flow rates increased from a mean of 9.3 to 13.4 (12 M), and 13.1 (24 M). Improvement in symptom score and peak flow was observed across all prostate sizes. By 2 years, 15 patients had dropped out of the study, 8 for alternative treatment (6 TURP, 1 bladder neck incision, 1 urethrotomy) and 7 for administrative or other reasons. Treatment with the T3 device provides excellent improvement in symptoms, flow rates and patients satisfaction. T3 fulfills the criteria for an effective, minimally invasive, outpatient treatment for symptomatic BPH.

The prognosis of superficial bladder cancer in terms of recurrence and disease progression is related to the bladder tumor multiplicity and the presence of concomitant 'plane' tumors such as high grade dysplasia and carcinoma in situ (CIS). This study on 33 patients tries to demonstrate the interest of fluorescence cystoscopy in transurethral resection of superficial bladder cancer The method is based on the detection of the protoporphyrin IX (PpIX) induced fluorescence in urothelial cancer cells by topical administration of 5- aminolevulinic acid (ALA). The sensitivity and the specificity of this procedure on apparently normal mucosa in superficial bladder cancer is respectively estimated at 82.9% and 81.3%. Thus, fluorescence cystoscopy is a simple and reliable method in mapping the bladder mucosa, especially in case of multifocal bladder disease and it facilitates the screening of occult dysplasia.

The deposition, and distribution of light in laser irradiated tissue are important in determining the extent of tissue injury during laser prostatectomy. As tissue is irradiated, the optical properties change as a function of temperature due to an alteration of molecular and cellular structure. An increase in the absorption or scattering coefficient may prevent light from penetrating deeper into tissue, thus compromising laser treatment. The purpose of this study was to determine if temperature affects the optical scattering and absorption coefficients of canine prostate tissue. The effects of freezing of tissue prior to measurement were also investigated. A double integrating sphere spectrophotometer was used to measure reflectance, and transmittance of laser light in canine prostate at two wavelengths. Optical properties were calculated using an inverse adding-doubling algorithm. Measurements were made on samples heated for ten minutes in a waterbath at 10 degree increments from 35 to 55 degrees Celsius, and 5 degree increments from 60 to 85 degrees Celsius. In general, absorption and anisotropy coefficients decreased slightly with increasing exposure temperature up to 65 degrees Celsius, then increased sharply. Scattering coefficients increased slowly from the baseline temperature to 60 degrees Celsius, followed by a sharp increase between 60 and 70 degrees Celsius. The scattering coefficient appeared to decrease at higher temperatures. Freezing the tissue prior to making the measurements resulted in a higher estimate of (mu) _a, (mu) _s, and g. These results were also found to be dependent upon the wavelength investigated. Results from this study indicate that as tissue is coagulated, thermally induced changes in the optical properties will limit the depth of penetration of light into the tissue.

The purpose of this study is to measure the effects of different working instruments (EHL probes, baskets, and graspers) and holmium laser fibers on deflectability in a variety of actively deflectable flexible endoscopes. A bench top study was performed to determine the effects of working instruments and laser fibers on a variety of actively deflectable flexible endoscopes. Baseline deflection was measured with and without working instruments in the working channel and compared between various flexible endoscopes. In ureteroscopes, 1.6 F and 1.9 F EHL probes decreased deflection minimally (0 - 34 degrees). Working instruments larger than 1.9 F had a greater effect upon deflection (33 to 90 degrees). Improved deflectability was noted with the 200 micron holmium laser fiber compared to the 365 micron fiber. The diameter of the working instruments did not affect deflectability as severely in cystoscopes compared to ureteroscopes. No significant differences in deflection existed between the 365 micron and 200 micron holmium laser fibers in the flexible nephroscopes tested. In summary, working instruments less than 1.9 F and the 200 micron holmium laser fiber have little effect on deflectability. This may result in improved access to lower pole and dependent calyces. Flexible cystoscopes with their larger working channels and stronger deflection cables are less affected by working instrument diameter compared to flexible ureteroscopes.

The laser-induced interstitial thermo-therapy of brain tumors requires an exact therapy planning. Therefore, the knowledge of the optical properties of native (na) and coagulated (co) tissue structures is important. In this study the optical properties of native and thermally coagulated (2 h, 80 degree Celsius) human white (n equals 14; na equals 7, co equals 7) and gray matter (n equals 14; na equals 7, co equals 7) were investigated (spectral range equals 360 - 1100 nm, spectral resolution 20 nm) in vitro using the integrating sphere technique combined with the inverse Monte-Carlo method. The (mu) _a of the native gray matter decreased from 0.333 plus or minus 0.219/mm (360 nm) to 0.054 plus or minus 0.069/mm (1100 nm). The (mu) _s varied between 14.13 plus or minus 4.26/mm (360 nm) and 5.53 plus or minus 1.80/mm (1100 nm). The g-value increased from 0.818 plus or minus 0.093 (360 nm) to 0.904 plus or minus 0.051 (1100 nm). Coagulation increased (mu) _a and (mu) _s by a factor up to 3 and g up to 16%. White matter exhibited a (mu) _a between 0.253 plus or minus 0.055/mm (360 nm) and 0.100 plus or minus 0.052/mm (1100 nm) and a (mu) _s between 40.20 plus or minus 9.18/mm (360 nm) and 28.65 plus or minus 6.83/mm (1100 nm). The g-value varied between 0.702 plus or minus 0.093 (360 nm) and 0.886 plus or minus 0.012 (1100 nm). Coagulation increased (mu) _a up to a factor of three and the g-value up to 14% while the increase (approximately 1.25 fold) of (mu) _s was not significant. We conclude the optical properties of human brain tissue change significantly due to thermal denaturation.

The knowledge of the optical properties of human tissue is indispensable for the understanding and optimal use of laser applications in medicine, especially for dosimetrical questions in laser-induced thermotherapy of liver metastases. In addition photothermal therapies have to consider the dynamic behavior of optical properties. In this study we evaluated the optical tissue properties of normal human liver tissue and of colorectal liver metastases. We used the double integrating sphere technique and the inverse Mont Carlo- simulation for evaluation of the optical properties. We were able to demonstrate significant differences between native and coagulated tissue as well as between normal and metastatic tissue. In the investigation of the dynamic temperature behavior of optical properties we could demonstrate that the coagulation rate cannot be described by a linear model.

We describe the design, and development of an infrared detection system which detects the onset of carbonization of fluoropolymers in the presence of up to 60 watts of 1.06 micrometer laser energy. This system is used to shut down a therapeutic laser system before significant damage is done to a laser delivery device and patient. Black body radiation emitting from the diffusion tip is transmitted, backwards, through the same optical fiber as the therapeutic wavelength. Using a high power 1.06 micrometer laser mirror at 45 degrees, most of the 1.06 micrometer light is reflected while the black body radiation is passed to a holographic notch filter which further filters the signal. Still more filtering was needed before the 1.1 to 2 micrometer signal could be detected within the presence the therapeutic light using an extended indium gallium arsenide photodetector. There was still a significant detected offset which increased with laser power which necessitated a means to automatically null the offset for different laser power settings. The system is designed to be used with any unmodified laser system. It interfaces directly to or in series with most common external safety interlocks and can be used with various diffusing tips, probes or bare fibers.

A line of optical fiber based diffusing tips has been designed, developed, and tested that are capable of distributing tens of watts of cw laser power over lengths ranging from two millimeters to over 10 cm. The result is a flexible non-stick diffuser capable of coagulating large volumes of tissue in reasonably short exposures of 3 - 5 minutes. Sub-millimeter diameter devices have a distinct effect on reducing the force needed to insert the applicator interstitially into tissue. Utilizing our design approach, we have produced diffusers based on 200 micrometer core fiber that has delivered over 35 watts of Nd:YAG energy over diffusion lengths as short as 4 mm. These applicators are being tested for applications in oncology, cardiology, electrophysiology, urology and gynecology.

In this study, the optimal combination of laser power and mutual fiber distance was assessed in order to take full advantage of simultaneous multiple fiber application in interstitial laser coagulation. For cylindrical diffusing fibers ((Theta) equals 600 micrometer, 2 cm diffusing length) were positioned in porcine liver tissue at a mutual distance of 1 - 4 cm. Nd:YAG laser light (lambda equals 1064 nm) of 4 - 7 W was guided through each fiber. By varying exposure time for the different power levels, energy applied was constant at 1800 J. The output of the four channels was measured with an output meter at various laser power levels with variation never exceeding 5%. After laser application the livers were sectioned and the zone of coagulation was measured in three directions; fusion between the coagulation zones surrounding the fibers was noted. Spherical lesions up to 5 cm (Theta) could be produced at the optimal settings of 7 W with a distance between the fibers of 2 cm. Mutual distances less than 2 cm resulted in smaller lesions with central carbonization and at larger distances no fusion between the four coagulative zones occurred.

For a minimally invasive treatment of pathologic tissue, e.g. tumors, the benign prostate hyperplasia (BPH) or the concha hyperplasia in otorhinolaryngology (ENT), next to the laser- induced interstitial thermotherapy (LITT) or the monopolar HF- surgery the interstitial thermotherapy with high-frequency alternating current (HF-ITT) in bipolar technique is a good alternative. Investigation results are presented which prove the feasibility and show the performance of this technique. Bipolar needles of different geometries, adapted to the various application fields, such as palliative treatment of metastatic carcinomas in liver and concha hyperplasia, were built and tested. Basic investigations of the thermal field distribution in in vitro samples were performed. The efficiency of the developed applicators were examined in in vitro experiments with porcine liver, turkey breast and porcine concha. Coagulation volumes of different needle diameters and power settings are show. Carbonization and dehydration can be avoided by irrigation of the tissue during treatment through integrated flushing ports and thus the performance is increased. For the treatment of concha hyperplasia special designs are presented which could probably offer an additional increase of safety and a simplification of performing a concha coagulation procedure. The new design of a bipolar needle electrode permits the surgeon the use of a partial application of high frequency current for ITT. Less power is needed due to the limited current distribution at the immediate operation site, which means that it is not necessary to fix the neutral electrode to the patient. Thus an easy to handle and a highly safe procedure can be performed by the surgeon.

In this study the effect of hepatic blood perfusion on lesion size, produced with Nd:YAG interstitial laser coagulation (ILC) was investigated. In 10 pigs the liver was exposed at a thoracolaparotomy. Lesions (n equals 23) were created with 4 cylindrical diffusing (2 cm length) fibers applied simultaneously (5 W per fiber, 6 min). There were three experimental groups: (1) with flow through the liver, (2) with portal vein clamped, and (3) with both hepatic artery and portal vein clamped. Immediately after sacrifice, the liver was dissected for macroscopic and microscopic assessment. The coagulated volume with flow (mean 6.5 cm³) was considerably smaller than with partial flow (30.6 cm³) and non flow (26.6 cm³). No significant difference was found in coagulated volume between the partial flow and non flow condition. Fusion of the coagulation zones surrounding the fibers was always found under partial flow and nonflow condition whereas this was never the case under the flow condition. This study shows the importance of occluding the portal flow during ILC.

The purpose of the study was to evaluate Gd-DTPA-enhanced MRI for the follow-up of laser-induced thermotherapy (LITT) in the treatment of liver metastases. Interstitial laser-induced thermotherapy (LITT) was performed in 55 chinchilla bastard rabbits with a Nd:YAG laser and a specially developed diffuser tip applicator. The animals were examined at different times using MRI and histological methods. T1-weighted spin-echo sequences were made with gadolinium-DTPA and submitted to correlation analysis. The analysis yielded a good correlation (r equals 0.96) between the largest lesion diameters. Lesions showed discontinuous regeneration kinetics with a 41% volume reduction 1 month after LITT. MRI of the lesion directly after LITT showed a hyperintense transition zone. Following the application of intravenous contrast medium, transition zone enhancement was first seen 72 - 96 hours after LITT. Even after 6 months, the laser-induced lesion is visualized as a non-enhanced area. Lesion regeneration followed the principles of wound healing. It is concluded that gadolinium-DTPA- enhanced MRI yielded definitive criteria for the follow-up assessment of LITT.

Adenomyosis is a condition in which the myometrium is infiltrated by endometrial glands and stroma. This results in myometrial hyperplasia, uterine enlargement and causes menorrhagia, dysmenorrhoea and dyspareunia for which there is no known cure other than hysterectomy. The success of LITT in the treatment of uterine leiomyomata suggested that this might also be effective for the treatment of adenomyosis. Initially LITT was carried out on patients with adenomyosis prior to hysterectomy, then on patients who had completed child-bearing and finally on those who desired a family. Not only were symptoms relieved but pregnancies occurred spontaneously. The KTP 532 nm component of the KTP/YAG laser, which is absorbed by red pigment, was used with a 600 micrometer fiber with a bare tip via a needle microstat at laparoscopy. Holes were drilled in the abnormal tissue 3 cm apart and the laser fiber then slowly withdrawn, the object being to coagulate the surrounding blood vessels and adenomyotic tissue. The number of joules required depended on the volume of tissue treated.

The success of treating tumors of the liver under local anaesthesia and ultrasound and computered tomography control by mens of the diode laser of 810 nm wavelength with fiber splitter and multiple fibers suggested this form of LITT might be suitable for the treatment of very large leiomyomas where laparoscopy was not possible. The immediate effect of LITT was to produce a large volume of coagulation within the myomas, to destroy the oestrogen receptors and to coagulate the surrounding blood vessels. After one month the coagulated volume had been converted into a jelly-like substance and the zone surrounding this had started to degenerate because of the destruction of its blood vessels which had resulted in local tissue anoxia. Three months later the central coagulum and surrounding zone had been partially absorbed and the whole volume of myoma treated had shrunk to a quarter of the original size. It has thus been shown that a minimally invasive method for the destruction of very large uterine leiomyomas can be safely performed, but further research is required before its general adoption.

Approximately 750 leiomyomas of 250 symptomatic patients were treated by LITT over a five-year period. Only 12% were lost to follow-up. Most were treated by a combination of the KTP/YAG laser, rarely by one or the other alone, and a few with the diode laser. The fiber optic was inserted 2 cm apart and, depending on the size of the tumor, 480 - 20,000 Joules were required. Most were treated laparoscopically but very large myomas were treated percutaneously under ultrasound control. Symptoms were nearly always relieved and the six failures were found to be due to unrecognized adenomyosis and other associated pathology. Half the patients complaining of infertility became pregnant and, in those whose only pathology had been leiomyomas it approached 90%. Vaginal delivery was not found to be contraindicated. Finally, oestrogen receptors and epidermal growth factor were found to be destroyed. It is concluded that LITT enables leiomyomas of all sizes and locations to be treated by a minimally invasive method with preservation of the uterus.

In order to better develop ultrasonography for use in monitoring interstitial laser therapy (ILT), we imaged rat mammary tumors using power Doppler ultrasound in conduction with intravenous contrast agent (Albunex) before and after laser therapy. Small vessel perfusion throughout a variable portion of the tumor could be detected by power Doppler ultrasound. Lesions created with diode laser by delivery of 500 to 3000 J appeared as perfusion defects on post-treatment images. Image topography and lesion size correlated with gross histologic findings. We conclude that ultrasonographic monitoring of local changes in blood flow using contrast enhancing agent can be useful in characterizing lesions created with ILT.

Although lasers have proven to be valuable in neuroendoscopy, surgeons still do not feel comfortable using high-energy laser endoprobes in close proximity to vital structures. A special laser catheter was developed with an atraumatic ball-tip which was pretreated with a layer of carbon particles absorbing 90% of the energy. The temperature at the surface of this 'black' tip reaches ablative temperatures instantly at powers of only a few watts within one second. This drastically limits the laser power and the length of exposure needed, increasing safety, even around critical structures. The characteristics of the 'black' tips were studied using a thermal imaging technique, showing heat just in front of the tip in contrast to uncoated fiber tips. These 'black' tips were applied in combination with Nd:YAG and diode lasers in 41 patients and a variety of procedures: third ventriculocisternostomy (n equals 27), cyst fenestration (n equals 8), colliod cyst resection (n equals 5) and fenestration of the septum pellucidum (n equals 1). Power ranged from 0.5 to 5 W and the average total energy for ventricular fenestration was 160 J. There was no mortality, nor increased morbidity. The procedure success rate was 100% and the overall outcome success rate was 90%. 'Black' atraumatic ball-shaped fiber tips are safe and effective in a variety of neuro-endoscopic procedures. Due to the low power range of only several watts, compact diode lasers are the energy source of first choice.

The paper deals with the analysis of the voice function in patients with laryngeal pathology who had undergone Nd:YAG contact laser surgery. Surgery technique is believed to be gentle and sparing not only structurally but also functionally. It was shown that the methods of function evaluation of phonation such as the voice dynamic range, the main tone testing, transient characteristics of speech tracing, spectrography and electroreolaryngography can serve as a helpful tool in diagnostics and treatment follow-up. Benign laryngeal growths, cysts, scarring, hypertrophic laryngitis and cancer tumors comprise an essential group leading to phonation disturbances. In recent years essentially new surgical approaches have been initiated in the management of these pathologies. It is assumed that voice function quality is dependent not only on the nature, extent and site of the pathology but, also on the technique of the surgery employed and, consequently, on the degree of operative trauma. Contact laser excisions are, among modern sparing methods of laryngeal surgery. It has been shown that contact laser methods are more advantageous as compared to conventional surgery. The present investigation is aimed at exploring phonation in patients with various laryngeal pathology after Nd:YAG contact laser surgery.

The aim of the present animal experimental study was to investigate the effect of temporarily interrupting hepatic perfusion as well as the application mode on inducible coagulation volumes. Experiments were carried out using a Nd:YAG-laser at a wavelength of 1064 nm. A special multifiber optical component was used. Ten German hybrid pigs served as the experimental animals. All animals were sacrificed four hours after the end of application, and the livers were removed for histological examination. With a single application, a mean lesion volume of 2503 mm³ resulted from a total applied energy of 4356 J. Under temporary occlusion of hepatic circulation a lesion volume of 7452 mm³ was found (p less than 0.01). Multifiber laser application with hepatic circulation led to a mean volume of 14612 mm³. During interrupted circulation, overlapping tissue lesions with a mean volume of 50285 mm³ were induced (p less than 0.01). Microscopic examination showed that the rim seen macroscopically was identical. As well the application mode as the hepatic circulation are statistically significant parameters for the inducible lesion volumes. The interruption of the liver perfusion during laser application led to a significant increase of the hyperthermically induced tissue lesion for single- and multifiber applications.

Basic histological data involving the UltraPulse carbon- dioxide laser has shown that layers of tissue measuring 50 - 100 (mu) may be ablated per pass, for passes one to three, leaving a similar layer (less than 100 (mu) ) of tissue necrosis. Clinical usage has suggested a decreasing level of ablation per pass with the maximum depth of ablation achieved with the first pass involving the epidermis. Each subsequent dermal pass appears to ablate successively less tissue with little visible tissue effects occurring after 3 or 4 passes total. At this point in treatment if instead of using single pulse tissue impacts, pulses are stacked one on top of another, a new threshold is reached whereby deeper dermal ablation is achieved. It is not known how many pulses (at 10 Hz) must be accumulated to reach this threshold of deeper ablation, nor is it known what happens to the layer of thermal necrosis associated with this pulse-stacking technique. A study was devised to evaluate the effects of 10 consecutive passes of single pulse vaporization regarding depth of vaporization as well as thickness of residual thermal necrosis. The same study was repeated regarding the tissue effects of 2 pulses at 10 Hz and 3 pulses at 10 Hz per pass for 10 passes

Newer carbon-dioxide laser systems incorporating short pulse and scanning technology have been used effectively to resurface the skin. Although scarring is rare, as the number of resurfacing cases has increased, some hypertrophic scarring has been observed. Previous dermabrasion and continuous wave (cw) carbon-dioxide studies suggest that depth of injury and/or thermal damage are important predictors of scarring for a given anatomic region. To determine if overlapping laser pulses/scans significantly altered wound healing, we examined residual thermal damage, cell death, and histologic and clinical wound healing in a farm pig. The Ultrapulse and SilkTouch systems were used with various radiant exposures, degrees of overlap, and numbers of passes. Thermal damage was assessed by histology, and dermal cell viability was measured with nitrotetrazolium blue staining. Presence or absence of clinical scarring was determined by noting textural change and loss of skin markings. We observed that thermal damage and cell death depth did not increase significantly with pass number; however, by double-pulsing or double-scanning sites, residual thermal damage and cell death depth were increased as much as 100% over areas without immediate overlap of laser impacts. Also, scarring was increased focally in areas with overlap. We conclude that immediate overlapping of carbon- dioxide laser pulses/scans is a significant risk factor in increasing thermal damage, cell death, and scarring.

The treatment of primary breast cancer in the last half century has progressively decreased in its disfiguring consequences while maintaining the same level of cure. Extending this philosophy beyond lumpectomy, we propose to treat small primary breast cancers by laser interstitial therapy with minimal possible cosmetic distortion. Our program to achieve that goal has made considerable progress in the preclinical instrument modification and development of physical, tissue, and live animal models. In anticipation of a clinical trial this report updates information presented in 1996.

A new Fourier transform infrared fiberoptic evanescent wave (FTIR-FEW) spectroscopy method has been developed for tissue diagnostics in the middle infrared (MIR) wavelength range (3 to 20 micrometers). Specific novel fiberoptical chemical and biological sensors have been studied and used for spectroscopic diagnostic purposes. These nontoxic and nonhygroscopic fiber sensors are characterized by (1) low optical losses (0.05 to 0.2 dB/m at about 10 micrometer) and (2) high flexibility. Our new fiber optical devices can be utilized with standard commercially available Fourier transform spectrometers including attenuated total reflection (ATR) techniques. They are in particular ideally suited for noninvasive, fast, direct, sensitive investigations of in vivo and ex vivo medical diagnostics applications. Here we present data on IR spectra of skin tissue in vivo for various cases of melanoma and nevus in the range of 1480 - 1800 cm^-1. The interpretation of the spectra of healthy and different stages of tumor and cancer skin tissue clearly indicates that this technique can be used for precancer and cancer diagnostics. This technique can be designed for real-time and on-line computer modeling and analysis of tissue changes.

We compare Los Alamos numerical simulations with Oregon Medical Laser Center laser deposition experiments conducted with gelatin thrombus surrogates specifically chosen for relevance to clinical laser thrombolysis. Initial idealized calculations suggest that a surprisingly large fraction of the absorbed laser energy appears as acoustic radiation. We build on these results here by investigating geometrical affects, material property variations, and sources of dissipation including viscosity and plastic flow, as well as acoustic radiation, in an effort to explain flow effects observed in the experiments. In particular, strong jetting is observed in the simulations when the gelatin is given a kinematic viscosity in excess of approximately 1.0 cm²/s. Jetting is clearly evident in the experiments.

We describe a simple and robust alternative to ultrasonic methods for the measurement of pulse propagation velocity (PWV) which detects the passage of the diameter wave as it passes two sites a known distance apart. Two probes each containing an infra-red emitting diode and a phototransistor are placed on the skin near to the vessel of interest. The energy returning to each probe depends on the amount of blood the beam has passed through, and this varies as the vessel pulsates. The output from each probe is displayed in real time on a portable PC. PWV is estimated beat-by-beat from the delay between the start of the systolic upswing in the signals from the two sites. In order to verify that our device measures changes in arterial diameter its signals were compared to those obtained simultaneously from an echo tracking pulsed ultrasound system. Transit time measurements from the two devices on the radial and femoral arteries in 6 subjects agreed closely. Additional validation experiments on 21 subjects undergoing cardiac catheterization have shown that transcutaneous measurements of PWV using the infra-red device agree well with intra-arterial measurements obtained with a cannula and pressure transducer. We conclude that the optical technique for measuring PWV is a useful addition to the methods available for determining blood vessel elasticity. Its simplicity and ease of use make it suitable for large scale measurements in the 'field.' Three such studies are currently in progress.

Laser irradiation use for treatment of different manifestations of oral mucous diseases during the last 10 years. The aim of this research was study of the results of use He-Ne laser radiation in combination with main therapy for treatment of oral mucous lesions of different aetiology. He-Ne laser irradiation use for radiation of lesions were caused by different aetiology reasons. Under the observation was 116 patients 20 - 64 years old, who had and hadn't background pathology. There were biochemical, immunological controls. Data of research confirmed positive effect of use He-Ne laser radiation.

Laser induced interstitial thermotherapy is a new minimally invasive procedure for the treatment of benign prostatic hyperplasia. In this study Ho:YAG laser induced lesions were investigated on liver, kidney and prostates of canines. While the dependency of the induced lesions on the energy/pulse at a constant mean power had been investigated on the liver, the dependency on the pulse duration was studied on the kidney. Additionally the dependency of the lesions induced on the total applied energy at optimized parameters had been determined in prostate tissue. In all experiments it could be demonstrated that interstitial pulsed Ho:YAG irradiation resulted in a cavity surrounded by a coagulation zone. The results show that changing the pulse duration by a factor of two or changing the energy/pulse at a constant mean power result in no significant alteration of the lesions sizes. These experimental findings may offer new treatment modalities with respect to interstitial laser therapy of BPH without damaging the urethra.

Influence of pulse energy, duration and beam cross-section on the outcome of Er:YAG laser ablation of skin is interpreted on the basis of an analytical model of heat diffusion and ablation front dynamics. Derived expressions enable us to identify different ablation regimes in terms of ablation efficiency and depth of thermally affected tissue layer for any thermally driven laser ablation process. Influence of laser wavelength is also discussed, focusing on a comparison between Er:YAG and carbon-dioxide laser skin resurfacing. Preliminary experimental and clinical evidence in agreement with the model is also presented.