Silica-core fibers have become a standard vehicle to remotely deliver ultraviolet to near- infrared light energy for medical applications. The three primary types of silica-core fibers commercially available for comparison are the Silica-clad, PCS soft-silicone clad, and TECS hard-fluoropolymer clad fibers. These fibers were evaluated on the basis of spectral transmission, numerical aperture, bend performance, strength, connectorization, and power handling. The results are presented and compared.

It is desirable in many surgical and industrial applications of infrared (IR) lasers to employ a flexible fiber optic delivery system to conveniently distribute energy to remote locations. While many different IR fibers have been developed only a few are suitable for the delivery of laser power. The best fiber candidates for the high power CO2 laser are the hollow metallic and hollow sapphire fibers, and at Er:YAG laser wavelengths the fluoride glass and solid-core sapphire fibers offer the greatest promise. Hollow metallic waveguides have been used to deliver up to 2,600 W of cw CO2 laser power.

Experimental parameters, as well as chemical and morphological parameters, were investigated with the purpose of improving the performance of the previous type plastic hollow fibers. The dielectric layer was identified as (beta) and (gamma) AgI. The dielectric layer thickness (t) was measured and was found to be dependent on the iodination time (T) according to the relation t equals T0.37. The thickness of the dielectric layer influenced the transmission through the hollow fiber by shifting absorption maxima and reducing the smoothness of AgI layer. The best focal lens of the coupling lens (ZnSe) was found to be 200 mm, and the colinearity angle between the beam and the fiber could deviate +/- 5 degree(s) from O degree(s) angle. The parameters of the new type of fibers were measured and found considerably improved. Employing cooling and pulse power reduced the heating and increased the lifetime of the fiber.

The Er:YAG laser beam has stronger absorbability by water than the CO2 laser beam. Therefore, the Er:YAG laser is expected to be used as the surgical treatment beam for water- rich biotissue. And if the effective optical fiber of 3 micrometers band is developed, it is also expected for use as an endoscopic beam. So we are doing investigations of the optical fiber for Er:YAG laser. The optical fibers used are fluoride glass, chalcogenide glass fibers, and the hollow tube guide. From our experimental results, these Er:YAG laser beam delivery techniques would be expected to perform well in practical use.

Medical applications of ultraviolet lasers are expected to produce new treatments. We have been doing the basic experiments of UV laser beam biotissue interaction with both KrF and XeCl excimer lasers for more than seven years. However, the optical fiber cannot be used for power UV beams. We have been investigating UV beams. We have tried beam delivery with OH ion-doped quartz fiber and a hollow tube guide. From our experimental results we found the influence of the Cl ions and the formation of defect in the quartz core by two photon absorption.

Laser power transmission experiments through silver halide discs and fibers have been performed. In these experiments cw, long pulsed and short pulsed (TEA) CO2 lasers, with power levels of 20 - 40 W or pulsed laser with energies of hundreds of mJ per pulse, have been used. The mechanical and optical properties of unclad fibers made of various alloys AgClxBr1-x with 0 < x < 1 were investigated. Compounds with x approximately equals .5 proved most suitable. They have optical losses of about .2 dB/m at (lambda) equals 10.6 micrometers and good mechanical properties.

In developing a better understanding of the requirements on optical fibers to make them more useful for medical and other applications where UV light/lasers are the preferred source, previous papers have dealt with all silica optical fibers. Here we describe the UV transmission of all the available fiber types; illustrating, for commercially available fibers, the effects of fiber type, core diameter, cladding thickness, and core OH level on this transmission. We also describe our first efforts to fabricate a new, modified hard plastic clad silica fiber with enhanced UV performance. Finally some of the remaining problems and concerns are identified and reviewed.

A percutaneous transluminal coronary angioplasty system using a unique combination of CO laser (5 micrometers ) and As-S infrared glass fiber under the guidance of a manipulatable laser angioscope catheter is described. The ablation and guidance functions of this system are evaluated. The angioplasty treatment procedure under angioscope guidance was studied by in vitro model experiment and in vivo animal experiment. The whole angioplasty system is newly developed. That is, a transportable compact medical CO laser device which can emit up to 10 W, a 5 F manipulatable laser angioscope catheter, a thin CO laser cable of which the diameter is 0.6 mm, an angioscope imaging system for laser ablation guidance, and a system controller were developed. Anesthetized adult mongrel dogs (n equals 5) with an artificial complete occlusion in the femoral artery and an artificial human vessel model including occluded or stenotic coronary artery were used. The manipulatability of the catheter was drastically improved (both rotation and bending), therefore, precise control of ablation to expand stenosis was obtained. A 90% artificial stenosis made of human yellow plaque in 4.0 mm diameter in the vessel was expanded to 70% stenosis by repetitive CO laser ablations of which total energy was 220 J. All procedures were performed and controlled under angioscope visualization.

Power transmission of excimer laser radiation at 308 nm through waveguides is of growing importance in medical applications. The maximum energy densities achievable at distal fused silica optical fiber ends are limited by the surface damage threshold of fused silica and by photodegradation of the optical fiber material. Limitations due to the surface damage threshold at the front surface can be avoided by applying tapered fiber geometries. In order to minimize photodegradation effects color center formation caused by high energy UV radiation has to be reduced. This involves optimization of the fused silica material properties and the necessity of modifying the manufacturing processes. Measurements on all silica fibers at 308 nm wavelength (XeCl excimer laser) show different influences of core material manufacturing. Not only the overall decrease of transmission but also the dependence of transmission changes on the number of laser pulses and defect annealing are strongly affected. Consequences for improved performance of all silica optical fibers in angioplasty are demonstrated by measurements on specially produced samples.

Photodynamic diagnosis (PDD) and therapy (PDT) require light application devices which enable homogeneous illumination of tissue in hollow organs. Three techniques based on modification of the aperture of single fibers are presented mainly for use in urology and pneumology in combination with rigid and flexible endoscopes. All illumination systems allow for nearly entire illumination of the endoscope's viewing field. A microlens system is used for fluorescence diagnostic purposes in the lung. The system, consisting of two plano convex lenses in a condenser configuration, is attached directly to the fiber. The beam profile is optimized by ray tracing calculations. For fluorescence excitation of the tumormarker Photofrin II in the urinary bladder a 500 micrometers plastic fiber is used. The tip of the fiber is polished to a double cone with angles of 12 degree(s) and 7 degree(s). With this modification the aperture is increased by a factor of two. Photodynamic treatment of confined superficial tumors in the lung was successfully performed with a fused silica fiber coupled to the endoscope in a special adaptive device. In this procedure laserlight at 630 nm is guided through the optics channel of rigid endoscopes. A homogeneous circular illumination pattern is obtained following exactly the deflection angle of the endoscope.

Current medical instrumentation research at InterScience, Inc. is aimed at utilizing state of the art electro-optics in the development of a diagnostic fiber optic instrument capable of quantifying vibration patterns in real time. This work is in collaboration with the Division of Otolaryngology of the Albany Medical College. The innovative diagnostic probe system design involves the miniaturization of an electronic speckle pattern interferometry (ESPI) system through the use of fiber optic elements coupled with high speed image acquisition from a solid state matrix detector. Subsequent frame by frame processing produces a high quality three-dimensional spatial representation of the vibrational pattern. The diagnostic probe system is being developed for quantitative tympanic membrane and vocal cord vibration analysis. The significance of the introduction of this instrument to the medical community is the contribution it could make in the efficiency and effectiveness of the diagnosis of otolaryngological disorders. Specific applications include the evaluation of tympanosclerosis, stiffness related middle ear disorders, ossicular chain abnormalities, tympanic membrane replacement, vocal dysphonias, and early detection of laryngeal carcinomas, cysts, and phenomenological properties of mucosal wave dynamics. The current instrumentation research is focused on the production of a prototype system for clinical trials. This research is based in ESPI optical system development and miniaturization, system hardware and software development, and clinical design of the probe heads within anatomical limitations. Significant advantages of this diagnostic tool over currently used instrumentation and procedures are the real time capabilities of the instrument, the ability to quantify the vibrational pattern in time and space, and the possibility of establishing a database of patient history and disorder characteristics. Once fully developed and integrated into the clinical environment, this system will have a profound effect on the diagnostic capabilities of the otolaryngologist and other clinicians and researchers of communication sciences and disorders.

The feasibility of new forms of monitoring the fragmentation and ablation process through the plasma feedback signals in laser lithotripsy and laser angioplasty has been investigated. In laser lithotripsy it has been found that shock wave feedback monitoring is not as reliable as the plasma emission feedback monitoring. The plasma emission spectra indicate clearly plasma formation on calculi or calcified plaque, while an audible signal can be observed on targets such as dark tissue, catheter, and blood. This technique was successful in ex-vivo experiments in which calculi were inserted into pigs' ureter and then fragmented. Spectra were obtained in vivo indicating calcium abundance in calculi and the feasibility of real-time stone composition analysis. Ex-vivo gallstone fragmentation was also performed successfully under plasma spectra feedback monitoring. In laser angioplasty, in vitro experiments have shown a discriminative effect at laser pulse energies of 40 mJ or greater. Strong plasma spectra can only be observed from calcified plaque and not from normal artery tissue or fibrous plaque. The threshold for plasma formation on calcified plaque increases in blood compared to that in saline while the spectral structure becomes more specific. This study shows promising prospects for the technique in both laser lithotripsy and laser angioplasty.

An in vitro model was developed for application in studies of the optical and physical characteristics of flowing blood in rigid and flexible tubes (artificial vessels). The results indicate that both transmission and reflection of light are dependent on blood volume changes, orientation as well as deformability of the red blood cells. Light transmission and reflection in human blood showed a parabolic behavior at hematocrit levels. > 38% when plotted against blood flow. At both a low and high flow rate, the light transmission increased when compared to an intermediate flow where the transmission showed a minimum. The optical wavelength used also affected the light transmission and reflection in moving blood. The results from studies of blood in flow-through models are of importance for the understanding of the optical mechanisms behind the signal generation in photometrical measurement techniques.

Using a laser Doppler velocimeter (LDV) subcutaneous adipose tissue blood flow (AF) was recorded in the upright and supine positions in the upper and lower abdomen in 22 morbidly obese patients before gastroplasty. Age was 42 +/- 3 (mean +/- SEM), weight 135 +/- 7 kg, and body mass index (BMI) 51 +/- 3. Adipose flow expressed as mV was: supine, upper abdomen 647 +/- 23, lower abdomen 604 +/- 24; upright, upper abdomen 621 +/- 27, lower abdomen 607 +/- 29. AF was significantly more in the upper than lower abdomen (supine position) and AF was significantly lower in the lower abdomen upright than the upper abdomen supine. Regression analysis of age indicates that blood flow decreases in the lower abdomen so that in the supine position the difference between upper and lower abdomen AF increases. Similar analysis of BMI did not indicate significant trends. These data indicate that with morbid obesity there is lower tissue blood flow to the lower abdomen. This may explain why such patients may develop areas of painful ischemic necrosis in the dependent region of their anterior abdominal pannus.

A simple sensor used for remote detection of middle infrared radiation is presented. It is based on the use of cooled semiconductor detectors as a sensitive unit and middle infrared fibers for radiation transfer from investigated object to the detector. Sensors of this kind are promising for detection of radiation emitted by weakly heated objects, for measurements of their temperature and temperature gradients. The unit could be used in medical diagnostics, remote spectroscopy measurements, and chemical control.

Fiber-optic catheters currently in use make it impossible to solve the main problem of spectral fluorescence diagnostics and to provide the high accuracy and reproducibility of in vivo tissue fluorescence investigations. It is well known that fluorescence signal intensity is varied with distance and angle between the biological tissue and the distal tip of the catheter. Signal intensity also depends on the arrangement of light delivery fibers relative to light collecting fibers. Taking these things into account, we developed a design for catheters which allows them to perform the endoscopical diagnostics of tumors with substantial reduction of confusing influences. The new catheters have been tested in preclinical and clinical practice. Their design fits the requirements of certain diagnostic aims, but could also be specified for other applications: measurements of reflection and scattering characteristics of the object, plasma emission spectra (during lithotripsy or angioplasty), etc. There also are wide areas of possible applications for spectra measurements of gaseous, liquid, or solid substances in biology and chemistry.

Fiber optics are used in medicine in power transmission for therapeutic use as well as in signal transmission for diagnostics. Fibers are the key component of the applicators which find a wide and varied use. Applicators with optical fibers are part of the standard equipment used with the various continuous and pulsed medical laser systems. Recently, optical fiber applicators for the Er:YAG, CO, and CO₂ laser have become available. A combination of therapeutic and diagnostic fibers promises, for example in lithotripsy and angioplasty, not only to improve the safety level, but also to ensure the accuracy of the dosage and the precision of the laser energy applied. For the design of commercial fiber optic components a practical definition of the engineering damage threshold including a reasonable safety factor is given. With respect to this engineering damage threshold an overview of existing fiber technology with respect to the fields of application is presented and two examples of feedback systems to increase safety are discussed.

The advent of fiber optics has proven to be a great boom to diagnostic and therapeutic medicine. In some ways it even rivals radiology in the breadth of its applications and benefits. In fact, as in radiology which made the inner body `visible' as never before, fiber optic has also opened much of the internal human body to view. Such viewing has greatly enhanced the discovery and diagnosis of disease and pathology. After diagnosis the same instrumentation is often used to guide the appropriate therapy and to follow the body's progress through its treatment and cure.

The strongly forward directed and torch like beam profile and spatial irradiance distribution of a laser beam delivered by a fiber may be changed by modifying the fiber tip optically. This paper briefly reviews the optical and thermal properties of several modified fiber tips used in conjunction with various lasers.

Present-day technology enables transmission of high quality images via telecommunication networks at an acceptable price. This enables the transfer of medical images. In our project we work on the development of a remote consultation service for diagnosis of otorhinolaryngology patients. This is done by integrating endoscopic equipment with a network of conference studios operated by Norwegian Telecom. Signals from a video camera attached to the endoscope are compressed and digitized by a video codec prior to transmission to a remote institution via a 2 Mbit/s circuit. The receiver can see the endoscopic examination on a monitor and influence the control and movement of the endoscope by communicating over two-way sound and picture connection with the person operating it. The challenge is to tailor a new service based upon two separate types of technology, i.e., endoscopic and telecommunication technology. Both these technical systems work well alone, but can they work together to solve a medical need? The development of remote consultation services is dependent on both technology and the ambient conditions. The article is based on our actual tests and has its focus on technology description and preliminary results from our experience with remote diagnosing and diagnostic reliability.

The special considerations and constraints associated with the design of an angioscopic fluorescence imaging system are explored. These considerations include: choice of illumination, catheter design, detection system, data processing techniques, and display. A radiometric study that investigated tissue radiance, noise limitations, and resolution was undertaken and the results are reported. Other issues considered include fiber transmission, catheter diameter, and feature selection for multispectral imaging. A design based upon reasonable system requirements and currently available technology and equipment is presented. In addition, a multispectral data set was collected and analyzed using the Hotelling projector. The result is compared with a ` white-light' image and a total-fluorescence image. Angioscopic fluorescence imaging is found to be a feasible technique yielding a rich data set. This data set is found to possess great potential for achieving improved detection and characterization of atheromatous disease.

The limited field of view available with conventional endoscopes has restricted the extent to which a full assessment of an abnormality and its anatomical relationship to surrounding structures may be made. The purpose of this research is to design a prototype system of a new endoscope that allows for an increased field of view to be obtained when compared to traditional endoscopes. The design of the system utilizes a panoramic annular lens (PAL) to obtain an image of the 360 degrees surrounding the optical axis of the lens. PALs have been characterized and evaluated on a larger scale in previous work performed in our laboratory. In the development of a prototype panoramic endoscope, research has been performed in the design of an optical train utilizing a miniaturized PAL and in its integration with fiber optics to obtain a panoramic view of the interior of a cylindrical pipe. The annular image obtained with this system has been linearized using customized software routines to obtain a more conventional view.

Miniaturization of silica-based ultrathin imagefibers is needed to serve more medical applications in diagnostic imaging. However, by reducing the pixel element size rapidly, the imagefibers were found to have the characteristics of the single-mode imagefiber. The optical properties of the ultrathin imagefiber with the LP11 mode cutoff wavelength within the visible wavelength region, which is called the single-mode imagefiber, have been studied. The studies found that the property of wavelength selective propagation associated with single-mode ultrathin imagefibers can be applied to the field of biomedical diagnostic imaging as a fluorescence sensor.

Using an experimental fiberoptically guided CO₂ laser system, we performed lesions on fresh bovine retinas. These lesions were shown to achieve measurable immediate chorioretinal adhesion. This model implies the feasibility of utilizing a fiberoptic CO₂ laser probe in intraocular surgery for retinal detachment. The advantages of using CO₂ laser energy are minimal damage surrounding the desired lesion and its versatility as a coagulator and cutter. With further research we believe that the technical problem of delivery can be solved. The CO₂ endolaser holds promise for intraocular surgery.

For the detection of thrombosis the classical vein-occlusion test can be carried out. For this purpose a fiber optic sensor has been developed.

Seventy-three patients suffering from sialolithiasis were treated by endoscopically controlled, laser-induced lithotripsy (LIL). The non-sedated patients were treated under local anaesthetic with specially developed endoscopes with a diameter < 1.8 mm. A laser fiber was then positioned on the concrement which was finally fragmented while being monitored using a pulsed excimer laser (308 nm), a dye laser (504 nm), and an Alexandrite laser (755 nm). In all cases a complete fragmentation of the stone was achieved. This approach to laser lithotripsy of salivary gland calculi with endoscopic monitoring represents a novel method which permits an out-patient treatment under local anaesthetic with a minimum inconvenience to the patient. In `in vitro' experiments the effectiveness of the stone destruction (plasma formation rate, the number of pulses required to fragment the stone, and fragment size) were tested. The quantitative assessment of the fiber end surface during direct contact and the determination of the shape and size of the broken fiber pieces have been tested. A possibility to avoid the fiber wear was developed. It's called `Index Matching' and needs a special endoscopic integrated flushing system.

We have developed an otoscope which contains an optical fiber capable of transmitting CO₂ laser energy. Such a hand-held unit may prove useful in the treatment of acute otitis media and otitis media with effusion. We used crystalline fibers (0.9 mm diameter) capable of transmitting CO₂ laser energy. Four guinea pigs were anaesthetized. In one ear a laser myringotomy was performed using 7.5 watts for 0.1 seconds. The diameter of the myringotomy was 1.5 mm. In the other ear a similar conventional myringotomy was performed. After three weeks three laser and three conventional myringotomies were closed. On the average conventional myringotomies closed 50% sooner than laser myringotomies. Temporal bones from three guinea pigs were removed and sectioned according to accepted methods. No histological differences were found between ears. This experiment has proven the feasibility of using an otoscope for fiberoptically guided CO₂ laser myringotomy.

Image-guided stereotactic endoscopy has made possible the accurate viewing of deep-seated brain lesions through a limited space. The use of endoscopy for the resection of pathological lesions, however, remains difficult because of the limited number of surgical instruments and techniques applicable. The authors recently developed an open-system endoscopy using a stereotactic guiding tube with an open window. Through this window, the surgeon can freely manipulate various microsurgical instruments and employ such techniques as laser vaporization. Using this approach, more than 25 intracerebral tumors were resected either totally or partially with complete hemostasis under direct visualization. Since this approach is an image-guided surgery, it is indispensable to plan and simulate the operation pre-surgically based on computerized brain images and also to monitor the real-time coordinates of the manipulating sites intra-operatively. In this report, a new advancement in the computed stereotactic guiding system for this endoscopic surgery is described.

A flexible, hollow fiber for transmission of CO₂ laser energy has been developed. Various forms of this fiber have been in routine clinical use for the past two years. This hollow fiber technology has shown itself to be a practical, durable, and cost-effective means of beam delivery for both freehand and endoscopic applications.

Fiber-optic based laser delivery systems are one of the most important applications of optical fibers in the medical industry. Silica optical fibers are becoming a standard vehicle for laser transport into the human body. Two types of silica core fibers with polymer cladding or glass cladding are being considered. Optical fiber coatings play an important role in fiber strength, reliability, and biocompatibility. Three major coatings, such as organic (polymeric), metallic, and inorganic, are commonly used on optical fibers. The polymeric coatings include ultraviolet-cured acrylate, silicone, and polyimide; metallic coatings include aluminum, indium, tin, and gold; inorganic coatings include oxides, carbides, nitrides, and carbon. In the medical industry, polymeric coatings are widely used. Metallic and inorganic coatings on optical fibers also can be considered. This paper highlights the strength, fatigue, and biocompatibility of silica fibers with different coatings.

The use of laser radiation of 1064 nm (Nd:YAG laser) in interstitial laser therapy is coming of age. It is important to realize that the irradiation of tissue contributes to optical changes of the tissue. Consequently, the coefficients of the heat transfer function and the thermodynamic description of the energy balance budget in tissue are not constant. Regarding laser-induced regional hyperthermia non-linear behavior is observed. The heat transfer is estimated to be at multi parameter process. As a first result, a mathematical model is being introduced. The parameters of the model are derived from thermal and spectroscopic in vitro- and in vivo- measurements. Experimental findings of MRI and LIF correspond with the hyperthermal process of the mathematical model.

There are two general methods for analyzing the color of an object, visual and instrumental, and both are used in medicine. For many years it has been mainly the visual method that has been used for the examinations of patients, whereas color measurement instruments have been used in laboratories. This was due to the high cost of these devices, since they contained a monochromator or other high-precision parts. Furthermore, these instruments were `table models,' fairly heavy, large, and non-portable, and therefore, not easy to operate under clinical conditions. The application of new technologies and the latest hardware and software developments to color measurement systems/sensors has greatly simplified their implementation, increased their speed, and reduced their size and cost, so that colorimetric instrumentation is now practicable in many medical applications. Non-invasive clinical measurements, monitoring techniques, and determinations of very small color differences can now be achieved, giving much better opportunities for making correct diagnoses and identifying illnesses at an earlier stage.

Progressive miniaturization of flexible fiberoptic instruments has made it possible to perform atraumatic endoscopy of the Eustachian tube and tympanic cavity with an intact ear drum. By means of a special set of carrier- and balloon-catheters which are partly actively steerable, flexible microendoscopes with outside diameters of 290 - 700 micrometers are inserted through the nasal cavity into the nasopharyngeal opening of the Eustachian tube and carefully advanced into the middle ear compartment under permanent direct visual control. Second generation microendoscopes with outside diameters of 750 to 1000 micrometers are equipped with a one- direction tip-steering mechanism which allows deflection up to 90 degrees. In addition to it, the use of two special types of four-function scopes (outside diameter: 1.6 mm and 1.8 mm) fitted with a one-lumen working channel are presented. This new technique of `Transnasal Tubo-Tympanoscopy' (TTT) only needs local anesthesia, normally is performed on an outpatient basis, and is indicated for the diagnosis of any disturbances of the sound conducting apparatus (ear drum and ossicular chain) like chronic otitis media and oto-sclerosis and of those sensorineural hearing disorders on which -- until today -- only the traditional surgical tympanoscopy could provide morphological information on the pathogenesis of the hearing loss, e.g., on assumed round window ruptures. By this minimal invasive and minimal traumatizing method pathological alterations of the ossicular chain as well as obstructions in the cartilaginous and the osseous part of the Eustachian tube can be directly visualized.

In the field of otorhinolaryngology lasers, especially the 002 laser, sometimes the NdYag Laser, have been used for many years. However their application has been limited to easily accessible region e. g. diseases in the oral cavity, the oro- and hypoharxynx and the larynx. The upper air ways, especially the nose, the paranasal sinuses and the nasopharynx are narrow and hidden regions, which have proved a challenge to the optical and laser engineers and physicians.

Microendoscopy of the nasal cavities and the para-nasal sinuses is a new and atraumatical method to investigate these anatomical regions which were previously inaccessible for direct visual inspection due to their special topography. By means of superfine flexible and partly actively tip controllable fiberscopes the procedure only requires local anesthesia. Microendoscopes with outside diameters of 290 to 1600 micrometers are inserted through the natural orifices or ducts of the para-nasal sinuses partly guided by actively steerable microcatheters of 5 to 9 F. The eyepiece of the scope is connected with a chip-camera simultaneously carrying the endoscopic images onto a monitor system. This new procedure contributes to a better presurgical planning and risk assessment of endonasal sinus surgery and to the avoiding of repeated x-ray imaging during the therapeutic follow up of acute and chronic para-nasal infections. Furthermore, in combination with fiber delivered laser systems, it forms the basis and technical precondition for `minimal invasive laser-assisted microsurgery' of these anatomic regions.

Transtympanic endoscopy provides a unique opportunity to view, undisturbed, the contents of the middle ear. Flexible and rigid endoscopes with diameters of 2 mm and smaller are now available with adequate resolution to perform exploration of the middle ear. Endoscopes can be introduced through a myringotomy or an existing perforation in the tympanic membrane to examine the middle ear in the office setting, thus reducing the need for exploratory surgery.

Among the diseases of the major salivary glands, sialolithiasis is a frequent clinical picture. Until now the condition has nearly always had to be treated surgically. In rare cases, discharge can be achieved by acid stimulation of secretion. If located distally in the excretory duct, concrements may be removed by enoral lancing. If it is close to glands, e.g., in the knee of Wharton's duct or in the ductal part of the submandibular gland, extirpation of the gland including the stone is unavoidable. Besides wound healing problems and the occurrence of salivary fistulas, the main risk of surgery is injury to the nerves around the major salivary glands, e.g., the n. facialis or one of its branches, the n. hypoglossus, or the n. lingualis with consecutive paresis. Based on the clinical results of lithotripsy by laser-induced shock waves (LIL) applied to renal stones and ureteroliths as well as bilary duct and pancreas stones, we investigated the suitability of endoscopically controlled laser therapy for sialolithiasis.