Benign prostate hyperplasia (BPH) represents a major health problem in old men. In the present transurethral resection of the prostate (TURP) is the gold standard treatment for BPH. Although TURP is related to low mortality rates its mobidity is quite high. To evaluate the efficacy and safety of a new surgical treatment for BPH we undertook 30 patients with symptomatic BPH. All of them were submitted to a laser prostatectomy using a lateral delivery system (non contact) connected to a Nd-YAG laser font. The preoperative evaluation showed a prostate weight ranging from 30,5 to 86 grams (mean equals 42,5). The preoperative prostatic specific antigen (PSA) ranged from 0,9 to 10,2 ng/dl (mean equals 4.3). The International prostate symptom score (I-PSS) ranged from 16 to 35 points (means equals 23,58). The flow rate ranged from 0 to m 12.8 ml/sec (mean equals 4,65) and the postvoid residual urine from 20 to 400 ml (mean equals 100). We obtained follow-up in 20 patients. After three months after the procedure the parameters were: I-PSS from 4 to 20 points (mean equals 7,0) p < 0.05. Flow rate from 6,5 to m 19.4 ml/sec (mean equals 12,95) p < 0.05 and the postvoid residual urine from 17 to 70 ml (mean equals 30 ml) p < 0.05. No blood transfusion was required. The complications were persistent disuria in two patients, bladder neck contracture in one patient and urethral stenosis in one patient. We concluded that laser prostatectomy is a safe and effective treatment for BPH.

Visual Laser Ablation of the Prostate has been shown to be an effective treatment for the relief of bladder outlet obstruction secondary to benign prostatic hyperplasia. Dosimetry studies using the potato and live canine model are commonly used to advocate application of the Nd:YAG energy into the prostatic tissue. Questions have been raised as to the accuracy of tissue heat penetration in such models based on the scatter and diffusion caused by variations in blood flow and tissue differences from one prostate to another. Thus a study was done to evaluate differences, it any, in heat energy penetration caused by blood flow in the prostate. Mature canine prostates were lased in the (1) live dog, (2) euthanized dog, and (3) en bloc resected canine prostates immersed in a water bath of 101 degree(s)F. Prostates were lased using 60 watts for 60 seconds in the 2, 4, 8, and 10 o'clock positions. One prostate model was lased in the 8 and 10 o'clock positions while alive and then removed in bloc, immersed in a water bath at 101 degree(s)F and lased at the 2 and 4 o'clock positions. A third prostate, having been completely removed two days prior to lasing and frozen, was immersed in a water bath at 101 degree(s)F and lased. The findings indicate in the resected prostate loss of the ring of thermal damage, however, a zone of coagulative necrosis which is consistent with that seen in the live model. Thus blood flow does not appear to have a significant effect on Nd:YAG depth of penetration.

The treatment of Benign Prostatic Hyperplasia using the Nd:YAG laser is developing rapidly since the clinical introduction three years ago. In most cases a right angled fiber is used to deliver the laser light laterally towards the abundant prostatic tissue. The characteristics of these fibers differ, with regard to the angle at which the beam exits the fiber and the beam profile, resulting in a specific power density distribution on the tissue. During clinical use the characteristics of a fiber may change due to deterioration of the fiber tip. In this study the behavior of the various devices was monitored before and during clinical use with a special design power meter (Aquarius). The Aquarius measures the status of a right angled fiber in about fifteen seconds under clinical conditions, i.e., under water and at high input powers (40 - 80 Watt). In contrast with integrating sphere power meters specifically the primary beam is measured. The degree of deterioration of various fibers was quantified optically and thermally during clinical use. Devices using a metal mirror transmitted slightly less power than internal refraction based devices (80 versus 90 percent). The transmission of the various devices was not linear with the input power; at higher input powers (> 30 Watts) vapor bubbles, that developed at the tip of the device, decreased the transmission. During clinical use there was a large variation in decrease of transmission with regard to the total amount of energy transmitted through the fiber. However, at the end of a procedure the transmission had dropped to under 50%. The Aquarius is a powerful tool for evaluation and comparison of different laser prostatectomy devices both for clinical and experimental studies.

Herein, I report on my first 50 contact laser prostatectomies performed with the SLT Nd:YAG laser. The obstructed prostatic urethra is opened via contact laser vaporization of the obstructing adenoma. The average pre-op AUA symptom score was 22.9 (range 14 - 30). The average 3 month post-op AUA symptom score was 2.1 (range 0 -8). Eighteen of the patients had the foley catheter removed approximately 4 - 6 hours post-op and were discharged the same day. Thirty patients had the foley catheter removed the morning following surgery and were discharged. And two patients had the foley catheter removed the morning following surgery, but remained in the hospital for medical reasons unrelated to the TURP. Thus, 48 (96%) of the patients were discharged within 24 hours of admission. No patient had to be readmitted to the hospital for any reason. All patients were allowed to return to full activity within 24 hours of discharge. The average hospital cost for the 48 patients discharged within 24 hours was $DOL4,694. This compares to the average hospital cost of an electrocautery TURP of $DOL6-8000. In summary, contact laser TURP using the SLT Nd:YAG laser relived the symptoms of an obstructing prostate comparable to electrocautery TURP. However, these results were achieved with a much shorter hospitalization, a quicker return to full activity and at a lower cost.

The `gold standard' therapy for patients with symptomatic bladder outlet obstruction secondary to benign prostatic hyperplasia has always been electrocautery TURP. However, in patients with medical problems requiring chronic anticoagulation, this procedure is contraindicated due to the extreme risk of hemorrhage, both during the procedure and the immediate post operative period. With the recent development of contact laser prostatectomy the patient on chronic anticoagulation can safely undergo the procedure. Herein, I present a case of a 60 year old with significant bladder outlet obstruction yielding an AUA symptom score of 18. The patient had a history of multiple episodes of deep venous thrombosis of the left leg with three prior pulmonary emboli. He was maintained on chronic anticoagulation with alternating days of 3.5 mg. and 5.0 mg. of warfarin sodium (coumadin). Preoperative cystoscopy showed a 4 cm prostatic fossa obstructed by tri-lobar hypertrophy, with large kissing lateral lobes and visual obstruction from the verumontanum. The patient underwent a contact laser prostatectomy with the SLT Nd:YAG laser at 50 watts. There was minimal bleeding both during the procedure and in the immediate postoperative period. At three months post-op the AUA symptom score had decreased to 2. This case demonstrated that contact laser prostatectomy can be safely and effectively performed in patients on chronic anticoagulation.

This is a report on a modified technique for use of a contact laser for transurethral surgery to improve voiding in spinal core injury patients. To produce a channel for voiding, chisel sapphire tips are used to deliver adequate Nd:YAG laser energy to vaporize tissue blocking the urethral passage. We present data on 51 spinal cord injury patients (range 29 - 76 years) who had contact laser surgery in the past 22 months. Urodynamic studies showed detrusor sphincter dyssynergia in 82% of patients. On cystoscopic examination prior to surgery, 39% had associated enlargement of the prostate and/or bladder-neck stenosis. Thirty-one percent also had associated strictures in the bulbous urethra. For transurethral resection of the sphincter, a 12 o'clock incision was made by passing the contact probe repeatedly and/or buttonholing and then cutting the overlying tissue. For vaporization of the prostate and eradication of urethral strictures, the contact chisel probe was passed repeatedly over the surface and also buttonholes were drilled. The overlying tissue was incised with the laser chisel. The buttonhole technique expedited the procedure for creation of an adequate urethral channel for voiding. During surgery, there was minimal blood loss of about 25 - 50 ml per procedure except in 2 patients who lost 100 to 150 ml. All except 4 patients voided satisfactorily within 1 to 8 days (mean 2.7 days) when the catheter was removed following surgery. The initial 4 patients who did not void well are also voiding satisfactorily following repeat surgery.

Diode lasers are air-cooled, efficient, compact devices which have the potential of very low cost when produced in quantity. The characteristics of diode lasers are discussed. Their applications in interstitial thermal treatment of the prostate, and laser ablation of prostate tissues, will be presented.

We have studied 810 nm (Diomed, Cambridge England), 950 nm (Diolase, Endocare, Irvine CA), 980 nm (Dornier, Munich Germany), and 1000 nm (Cynosure, Bedford MA) using free beam right angle firing fibers in the canine prostate. Because some lasers only accept specific fibers, and each wavelength has its own divergence properties, standardization of fiber and power density was not possible. Power was studied in increments to the maximum output for each laser. Laser-tissue interaction was studied by video endoscopy during lasing, pathology, and real time interstitial thermometry at 3, 7, and 11 mm deep from the prostatic urethra. We found that using the Dornier Sidefocus fiber at 25 W, 810 nm created a small vaporized cavity surrounded by a zone of necrosis, whereas 980 nm at 25 W caused more necrosis but little vaporization. Irradiation with 950 nm and the Prolase II fiber created deeper lesions at 40 W than 25 W. At 1000 nm with the angle delivery device produced by Cynosure, popcorn with the formation of carbonized cavities occurred at both 25 and 40 W. The lesions were only slightly deeper at the higher wattage. We conclude that the high power diode lasers are capable of producing volume lesions in the prostate. The different wavelengths, fibers and power densities lead to different laser-tissue interaction, and thus each wavelength needs to be considered separately.

The objective of the study was to compare the extent of thermocoagulation induced in the human prostate by two regimens of Nd:YAG laser (50 W X 60 s and 15 W X 180 s) and one regimen of diode (810 nm) laser (15 W X 180 s). Powers were measured at the fiber tip. The study was conducted in 6 patients undergoing radical prostatectomy because of malignancy whose prostates were treated transurethrally with laser radiation at the time of the procedure. The prostate specimens were retrieved approximately 90 minutes after laser treatment, and then prepared for histological examination. In all the cases, the diode laser was applied to the left side of the prostate and the Nd:YAG laser (either regimen) to the right side, in order to prevent treatment variables related to histological composition. Coagulation necrosis was confined within the transition zone in all the case and at times BPH was unaffected, if nodular. Similar depth of coagulation was observed for both Nd:YAG regimens (mean 12 mm, range 10 to 14) and the depth of coagulation was slightly less for the diode laser (mean 10.6 mm, range 8 to 14). Our results suggest that, at the studied dosimetries, the thermocoagulation effect of diode laser in the human prostate approximates to that seen with Nd:YAG laser.

We investigated the use of the 805 nm diode laser (Diomed 25 Diomedics, The Woodlands, Texas) in combination with a cylindrically diffusing fiber (Surgimedics, The Woodlands, Texas) to perform visual laser ablation of the prostate in 8 mongrel dogs. Each dog received 15,000 J of laser energy delivered to the prostate in one continuous dose of 25 W for 10 minutes. Gross and histopathologic examinations of serial sections of the prostate were performed at intervals from 3 hours to 7 weeks postoperatively. All dogs did well postoperatively with only one episode of urine retention 5 days after the surgery. Grossly, an ellipsoid zone of destruction with an average maximum diameter of 2.1 cm was present in all dogs. Histopathological changes in the prostate were similar to changes consistently reported for prostatectomies performed with similar dosimetry utilizing the 1.06 Nd:YAG laser. We believe this wavelength laser in combination with the diffusing fiber compared favorably with the Nd:YAG/sidefire fiber studies previously done in this laboratory with the added advantage of simplified operator technique, less postoperative complications and increased margin of safety.

The objective of this study was to evaluate the effectiveness and safety of diode laser for the treatment of human BPH. The study included 11 patients with significant BPH that were treated with diode laser 15 watts for 180 seconds (Diomed, Inc., Gallium-Aluminum- Arsenide, 810 nm). Mean age was 69 years (range 59 to 84). Mean prostatic volume was 64.5 cc (range 30 to 96). In all cases the procedure was uncomplicated, the blood loss was minimal (< 100 cc) and all patients were discharged within the first 24 hours. On average, patients voided spontaneously after 4 days (range 1 to 11). There were no postoperative complications. At 6 months follow up the mean AUA-7 symptom score decreased from 24.27 to 8.12, the peak flow rate increased from 7.12 cc/sec, to 13.85 cc/sec, and the post void residual diminished from 58.5 cc to 38 cc. Our study suggests that diode laser therapy may offer a safe and effective alternative for the treatment of BPH.

As a possible solution to this problem, previous writers have suggested the possibility of treating BPH through interstitial thermotherapy. In this treatment, prostatic tissue is heated from within the prostate to the point of irreversible necrosis. Healing processes then reduce the volume of the affected tissue, even in the absence of sloughing. This study covers initial human use of such a device, using an 810 nm wavelength diode laser not previously used for such therapy.

The ideal surgical laser for the treatment of soft tissue pathology should possess both ablative and hemostatic abilities. As well, for use in urologic conditions the laser must also be suitable for endoscopic use. The Holmium:YAG laser possesses these qualities and in preliminary clinical use has demonstrated a variety of potential urologic applications. In this study we review our initial experience with the Holmium:YAG laser over a 18 month period. A total of 51 patients underwent 53 procedures for a variety of soft tissue conditions including: bladder tumor ablation (25), incision of ureteral stricture (15), incision of urethral stricture (6), treatment of ureteropelvic junction obstruction (3), incision of bladder neck contracture (2), and ablation of a ureteral tumor (2). Satisfactory hemostasis was achieved in all cases. Procedures were considered successful (no further intervention being required to treat the condition) in 81% of the cases. Two patients with dense bladder neck contractures required electroincision under the same anesthetic for completion of the procedure. A single complication, that of urinary extravasation following incision of a urethral stricture resolved with conservative management. In summary, the Holmium:YAG laser has demonstrated safety and proficiency in the treatment of a variety of urologic soft tissue conditions.

A variety of devices are currently available for intracorporeal stone fragmentation. Recently a new wavelength of laser, the Holmium:YAG, has demonstrated a variety of potential urologic applications including ablation of soft tissue lesions as well as stone fragmentation. This laser has a wavelength of 2100 nm and operates in a pulsed mode. Energy is delivered through a 400 um quartz end-firing fiber. In this presentation we review our clinical experience with the Holmium:YAG laser for the treatment of renal and ureteral calculi. Over a 23 month period, 63 patients underwent 67 procedures. Seven procedures consisted of percutaneous nephrolithotripsy for large or staghorn renal calculi. Sixty procedures were performed for ureteral stones. Procedures for proximal ureteral stones (6) employed a retrograde approach using flexible ureteroscopes (8.5 or 9.8). Stones in the mid ureter (12) and distal ureter (42) were approached transurethrally using a 6.9 rigid ureteroscope. Complete stone fragmentation without the need for additional procedures was achieved in 82% of cases. Treatment failures included 1 stone migration into the renal pelvis during laser activation, 6 patients who had incomplete fragmentation and 3 patients in which laser malfunction precluded complete fragmentation. Stone analysis available in 23 patients revealed calcium oxalate monohydrate (15), calcium oxalate dihydrate (2), cystine (2), uric acid (3) and calcium phosphate (1). A single complication of ureteral perforation occurred when the laser was fired without direct visual guidance. Radiographic follow-up at an average of 16 weeks is available in 22 patients and has identified 2 patients with ureteral strictures that are not believed to be related to laser lithotripsy. In summary, we have found the Holmium:YAG laser to be a reliable and versatile device for intracorporeal lithotripsy. Its safety and efficacy make it a suitable alternative for performing intracorporeal lithotripsy of urinary calculi.

It is shown that infra-red ((lambda) equals 1064 nm) long pulse (approximately 100 microsecond(s) ) radiation of YAG:Nd laser, operating in free generation regime, effectively fragments gallstones, urinary calculus and kidney stones. The features of the mechanism of this process are investigated. Laser lithotripsy is nowadays a method widely used for fragmentation of gallstones, urinary calculus and kidney stones. Flashlamp pumped dye lasers of microsecond duration are most often used for such purposes. Nevertheless, there are some reports on lithotripsies with nanosecond duration laser pulses (for example, Q-switched YAG:Nd laser). The mechanism of the laser fragmentation of such stones was supposed to be the next. The laser powerful radiation, delivered through the optical fiber, is absorbed by the material of the stone. As a result of such highly localized energy absorption, dense plasma is formed, which expands. Such plasma and vapor, liquid confined, forms a cavitation bubble. This bubble grows, reaches its most dimension and then collapses on itself in some hundreds of micro seconds. Shock waves generated during the growth and the collapse of these bubbles are the origin of fragmentation of the stone. It is necessary to say that there are rather confined data on the hundreds microsecond laser pulse fragmentation especially what concerns the usage of infra-red (IR) YAG:Nd lasers with long laser pulses. Clearing this problem would result in better understanding of the fragmentation mechanism and it could favor development of simple and more reliable laser systems for lithotripsy. In this work we report about investigation of features of an effective fragmentation of gallstones, urinary calculus and kidney stones under exposure of IR ((lambda) equals 1064 nm) radiation of repetitive YAG:Nd laser working in free generation regime.

The ability to vaporize extremely thin layers of epithelial tissue without any char and with minimal thermal necrosis is extremely advantageous in the treatment of superficial lesions of the external genitalia. We present a novel CO₂ laser `SwiftLase' flashscan technology capable of providing char free ablation of 3 mm diameter lesions with only 150 micron residual thermal necrosis depth at power level as low as 10 watts. These power levels are achievable with a small transportable CO₂ laser. The SwiftLaser is a miniature opto- mechanical scanner which homogeneously covers a 3 mm diameter surface with a 0.1 mm spot size focused beam within 0.1 seconds. The instantaneous beam's dwelling time is 1 millisecond. The instantaneous power density level at the focal point is higher than the threshold for char free ablation, thus providing a large char free ablation crater. Since depth of each ablated layer is 0.1 mm, the depth of treatment can be precisely controlled. The SwiftLaser technology has extensively and successfully been used in the last two years for the treatment of HPV in female lower tracts (Vulvectomy). The same technique may be performed with extramammary Paget's disease of the vulva, penile condylomata, and other epithelial disorders of the external genitalia without damage to surrounding healthy tissue. Technique and clinical results will be discussed.

We are reporting the preliminary results of a nonrandomized trial using a low-level gallium- aluminum-arsenide (GaAlAs) laser at a wavelength of 830 nm (Microlight 830, Lasermedics, Inc., Stafford, TX) to treat patients with symptomatic Peyronie's disease. All patients entered into the study had disease consisting of a well-defined fibrous plaque causing pain and/or curvature of the penile shaft on erection that interfered with satisfactory sexual intercourse. Treatment has consisted of 30 mW administered over a duty cycle of 100 seconds (3 J) beginning at the base of the penis and extending to the coronal sulcus over the dorsum of the penis at 0.5 cm intervals. An additional duty cycle of 100 seconds was delivered to each 0.5 cm of palpable plaque. The ability of the therapy to reduce the size of the fibrous plaque, the severity of the penile curvature, and the severity of pain associated with penile erection and the treatment's effect on the patient's quality of life were assessed for each patient at completion of therapy and 6 weeks later.

Early detection of prostatic cancer currently depends on Prostate Serum Antigen or TransRectal UltraSound. Unfortunately, these techniques are not always reliable indicators for early small lesions still localized within the prostate. This paper presents a feasibility study on the use of `tomographic needles and catheters' for optical imaging of early lesions. Three needles are inserted perianeally into the prostate or two catheters are inserted into the rectal and urethral passages. Each contains a set of optical fibers which terminate at evenly spaced positions along the needle. Each termination serves as either a source or collector for light transmission as each fiber is sequentially illuminated. Application of a tomographic algorithm based on diffuse light transmission between each source/collector pair yields a fuzzy but spectrally informative image of the prostate. This paper addresses the issue of feasibility by asking whether such a technique can distinguish a large zone of slightly alter optical properties (essentially a region of normal tissue) from a small zone of strongly altered optical properties (a tumor). The paper simulates both steady-state and 3-GHz frequency-domain optical measurements.

Electronic Speckle Pattern Interferometry (ESPI) is a nondestructive optical evaluation technique that is capable of determining surface and subsurface integrity through the quantitative evaluation of static or vibratory motion. By utilizing state of the art developments in the areas of lasers, fiber optics and solid state detector technology, this technique has become applicable in medical research and diagnostics. Based on initial support from NIDCD and continued support from InterScience, Inc., we have been developing a range of instruments for improved diagnostic evaluation in otolaryngological applications based on the technique of ESPI. These compact fiber optic instruments are capable of making real time interferometric measurements of the target tissue. Ongoing development of image post- processing software is currently capable of extracting the desired quantitative results from the acquired interferometric images. The goal of the research is to develop a fully automated system in which the image processing and quantification will be performed in hardware in near real-time. Subsurface details of both the tympanic membrane and vocal cord dynamics could speed the diagnosis of otosclerosis, laryngeal tumors, and aid in the evaluation of surgical procedures.

Autofluorescence characteristics of normal, dysplastic, and malignant squamous tissues from the oral cavity were measured with a spectrofluorometer in the excitation range of 250 - 500 nm and emission range of 350 - 750 nm. Fluorescence excitation-emission matrices (EEM) were obtained from samples collected from patients in the clinic and in the operating room. The same samples were submitted for histopathological examination following spectroscopic measurements. The contour plots obtained from the EEMs of the samples showed consistent differences between normal and abnormal tissues. All the abnormal samples showed enhanced red region (> 600 nm) fluorescence with a prominent peak at 635 nm, when excited by 410 nm light. A ratio contour plot (abnormal/normal) enhanced spectral differences in the red region. A fiber-optic based spectrofluorometer for EEM measurements is being developed for further investigations.

The major drawback in laparoscopic and endoscopic surgery is the loss of true 3D perception that is present in conventional surgery. An explosion in the number of minimally invasive surgical procedures highlights the need for improvement in visualization. Several manufacturers are working to develop monitor-based or head-mounted display for 3D visualization for minimally invasive surgery by combining emerging 3D endoscopes with visual immersion and head-mounted 3D stereo displays. One of them, Vista Medical Technologies, Inc., has developed a personal surgical monitor that offers a true 3D viewing when used with a 3D endoscope or a binocular viewing when used with a regular endoscope. This paper discusses advantages and shortcomings of this system on a background of emerging 3D endosurgical technology.

Interventional Video Tomography (IVT) is a new imaging modality for Image Directed Surgery to visualize in real-time intraoperatively the spatial position of surgical instruments relative to the patient's anatomy. The video imaging detector is based on a special camera equipped with an optical viewing and lighting system and electronic 3D sensors. When combined with an endoscope it is used for examining the inside of cavities or hollow organs of the body from many different angles. The surface topography of objects is reconstructed from a sequence of monocular video or endoscopic images. To increase accuracy and speed of the reconstruction the relative movement between objects and endoscope is continuously tracked by electronic sensors. The IVT image sequence represents a 4D data set in stereotactic space and contains image, surface topography and motion data. In ENT surgery an IVT image sequence of the planned and so far accessible surgical path is acquired prior to surgery. To simulate the surgical procedure the cross sectional imaging data is superimposed with the digitally stored IVT image sequence. During surgery the video sequence component of the IVT simulation is substituted by the live video source. The IVT technology makes obsolete the use of 3D digitizing probes for the patient image coordinate transformation. The image fusion of medical imaging data with live video sources is the first practical use of augmented reality in medicine. During surgery a head-up display is used to overlay real-time reformatted cross sectional imaging data with the live video image.

Differences in tissue autofluorescence between normal bronchial tissue and cancerous or pre cancerous bronchial tissue have been documented and exploited for the early detection of lung cancer (1,2) The larynx and nasopharynx have not been so well studied. Even with the most advanced fiber-optic equipment in experienced hands, the nasopharynx is an accessible but challenging area to examine. Small nasopharyngeal carcinoma are difficult to detect. For the larynx the challenge is the precise tumour localization which will allow more accurate staging of the malignant disease. The thought is that the tissue autofluorescence and tissue optical properties (absorption and scattering) which allow one to detect and localize early lesions in the bronchial tree may be similar in the larynx and nasopharynx and likewise exploitable for detection and delineation of lesions. The major characteristics of the autofluorescence properties of bronchial tissue, which may be found to be similar in other sites, are summarized below.

The vibration analysis of vocal cords gives information about the functioning of speech organs as well as about some illness within human organism. The analysis is usually performed by electroglottography or stroboscopic methods. The authors present the new opto-mechanical and electronic system of photolaryngoscope. The instrument uses laser diode light for illumination of vocal cords. The light reflected from the vibrating cord surface is detected electronically and analyzed. The further mathematical analysis of glottograms by autoregression method with covariance or by periodogram method is performed in order to define new criteria for medical interpretation of results.

Preoperative embolization and excision used to be standard therapy amongst a wide range of other more or less successful methods for the treatment of voluminous hemangiomas. Nowadays a combination of argon, tunable dye, copper vapor and Nd:YAG laser therapy achieves better cosmetic and functional results. Due to its limited penetration depth percutaneous laser therapy can only be utilized for superficial vascular malformations. Interstitial laser therapy, as performed with the Nd:YAG laser, allows treatment of voluminous hemangiomas in their full extent. The localization of these vascular lesions is evaluated by high resolution ultrasound with a new anular array scanner which ensures the precise intraoperative placement of the laser light fiber in the target tissue. Modified new light applicators improve the interstitial thermotherapy of hemangiomas. The tip design of the scattering-dome fiber allows diffuse circumferential irradiation with larger defined coagulation volume and minimized carbonization. Continuous intraoperative sonographic monitoring lowers the risk of damaging adjacent intact anatomical structures, helps to reach all tumor areas an to estimate the effect of the applied laser light caused by changes of sonomorphology. The postoperative outcome is evaluated by B-mode sonography and the new technique of ultrasound color angiography.

A Q-switched frequency-doubled Nd:YAG dye laser, tuned to 577 nm, was used to study the effect of nanosecond pulsed light on vascular tissue. Different reactions such as vasospasm, vessel expansion and vessel rupture were observed in living rats and were seen to be correlated with increasing fluence up to 3 J/cm². When it occurred, localized vessel rupture was seen on the irradiated side of the blood vessel, as well as on the opposite side. It was hypothesized that the damage on the backside of the blood vessel is the result of intense acoustic waves produced by strong absorption of the laser radiant energy in the first 30 micrometers of blood. Experiments were performed in vitro using cuvettes filled with diluted hemoglobin on which the 532 nm radiant energy produced by a Q-switched frequency-doubled Nd:YAG laser impinged. High-speed imaging of the irradiated air-blood interface using a time-delayed pulsed nitrogen-dye laser did not show evidence of cavitation micro-bubbles but did show the formation of a large, slowly expanding vapor bubble. Measurements of the acoustic waves produced with 12 mJ pulse in a spot size estimated to be 0.25 mm gave pressures up to 74 bars. Measurements at different positions with respect to the irradiation spot showed differences in acoustic amplitude that could not be explained by absorption attenuation. It is hypothesized that these differences are a result of differential diffraction of the frequency components of the acoustic wave, components of which extend up to a maximum of about 4 MHz. It is the highly directional high frequency acoustic energy that could be causing the damage on the side of the blood vessel opposite the point of irradiation.

The combination of the short penetration length in water and the delivery through flexible quartz fibers made the radiation of the Holmium laser very promising for minimal invasive surgery. Furthermore the available power density of 10⁶ W/cm² overcomes the threshold for ablation, which opens the way for cutting and removal of bone and cartilage, which is important for surgery especially in ENT. In contradiction, recently warning had been brought up that particularly in cartilage the damage zone can exceed the ablation zone by orders of magnitude and one should be restrictive using the Holmium laser for joint surgery. We found that the effect of Holmium laser radiation on tissue cannot be described by a pure absorption and ablation process. Experimental data showed that in the case of bone scattering has to be considered, and in the case of cartilage a remarkable heating of the remaining tissue occurred. This amount of heating could be reduced significantly by a new designed fiber mount, which cooled the tissue.

The CO₂ laser has been used by our group as a secure and efficient tool for the treatment of symptomatic oral cavity hemangiomas which can be responsible for disturbance for swallowing, phonation and in hygienic, besides discomfort and bleeding to patients. During the last four years, twelve patients with symptomatic oral cavity hemangioma were treated at the Laser Unit of our University. The treatment consisted in the application of CO₂ laser at medium to low intensity according to characteristics and location of the lesions. For hemangiomas located at sites of easy surgical access such as anterior 1/3 of the tongue, lips, bucal vestibule we use 10 to 37 J/mm² over the surface of the lesion. When the hemangioma was located at difficult surgical access sites, such as, tonsils, posterior 1/3 of tongue, or at pharyngeal wall we used 3.0 to 4.0 J/mm² encircling the whole hemangioma. This causes reduction in the size of the lesion throughout sclerosis of nutrition vessels. After this initial procedure we applied 0.8 to 1.0 J/mm² over the whole extent of the lesion. For both procedures we observed no significant bleeding or inflammatory reaction. The patients referred minimal post-operative discomfort with good cicatricial evolution. The evident reduction in the vascularization and size could be confirmed by photographic documentation. The good results described above, with disappearance of symptoms lead to the conclusion that CO₂ laser is an efficient and secure method of treatment for symptomatic hemangioma of the oral cavity.

The Nd:YAG laser 1.44 micrometers wavelength is a relatively new wavelength with water absorption coefficient higher even than 1.06 micrometers , permitting the creation of a more precise lesion with less damage to surrounding tissue. Very little, however, is known about its effects in live experimental model. The non-contact 1.44 micrometers Nd:YAG laser was used in four animals (dogs) to perform a resection of middle turbinate and to create a 1 cm lesion on the septal mucosa and inferior turbinate in the left side through a sinuscope. The same procedure was performed on the opposite side using microsurgical forceps as a control. The animals were followed-up, examined endoscopically, and sacrificed after 48 hours (1 animal), 1 month (1 animal) and 2 months (2 animals). Moderate-to-severe bleeding was commonly encountered on the control side, which obscured vision, and required packing in 2 dogs. In contrast, the laser had a satisfactory hemostatic result with easy control for endoscopic resection. Normal healing was observed under gross and by histologic examination 48 hours and 1 month after the surgery and healing was complete by 2 months. There was more scaring and adhesions produced by the forceps on the control side. Histologically, tissue thermal damage produced by the laser was superficial and confined to the lesion. The epithelial regeneration has been nearly completed in 1 month, with normal mucosa coverage in 2 months after the surgery. This study suggests that the 1.44 micrometers wavelength of the Nd:YAG should be considered as safe and reliable for intranasal application.

Laryngeal lesions such as papillomata can be removed with CO₂ laser but the scar that forms after repeated treatments can cause reduction in the function of the larynx. This scarring may be made worse by infection caused by interruption in the epithelial surface. It is hoped that if the vasculature of these lesions can be thrombosed without damage to the epithelium, the lesion will atrophy without the risk of infection and scar formation. A series of in vitro experiments were carried out to determine if the 810 nm high energy pulsed diode laser could be used to coagulate blood. Experiments with a laser fluence of 22 J/cm² on flowing and stationary animal and human blood in 750 micrometers diameter capillary tubes showed that single pulses caused a maximum detectable rise in temperature of 16 degree(s)C and no coagulation. Multiple pulses in slow flowing blood did generate a sustained temperature rise of 40 degree(s)C which may be enough to cause coagulation. Further in vitro and in vivo studies are underway to determine the clinical usefulness of this energy source.

10.6 micrometers CO₂, 2.01 micrometers Thulium:YAG (Tm:YAG) and 2.94 micrometers Erbium:YAG (Er:YAG) are currently being used or investigated for potential applications in otologic surgery. In addition to biologic tissue there are numerous synthetic materials (Gelfoam, Silastic, C-Flex, Silicone and Teflon), mineral components (Hydroxylapatite) and metals (stainless steel) that may be encountered during surgery. Their behavior in response to laser irradiation is, for the most part, unknown. We investigated the effects of these lasers, operated at clinically relevant parameters on these materials. We looked for signs of melting, perforation, charring, smoke formation and ignition. The results show that wet Gelfoam proved to be a partially effective barrier to all lasers. Silastic transmitted the energy of the Tm and Er:YAG with minimal damage, but charred, ignited or exploded with the CO₂ depending on the energy applied. All lasers melted C-Flex at higher energies. On Silicon, CO₂ produced flames, char and melting; the other lasers produced a tiny spark and less melting. Teflon charred and perforated when exposed to any laser, but only Tm:YAG produced a spark. All lasers at moderate and high energies shattered hydroxylapatite. Stainless steel was not affected by CO₂, but was perforated by Tm:YAG and Er:YAG. The results suggest that none of the tested lasers are safe for all currently used prosthetic materials and therefore they should be used with caution.

Despite aggressive surgical and radiotherapy, recurrence rates for patients with recurrent head and neck carcinomas remain high. Photodynamic therapy has been successfully used to treat patients with early carcinomas. This is due to the ability of the activating laser light to penetrate up to one centimeter into tissue, resulting in destruction of microscopic tumor with preservation of normal tissues. Employing this principle, PDT was used as an adjuvant intraoperative therapy following resection of tumor in five patients with recurrent infiltrating carcinomas of the head and neck. All patients tolerated the treatment without complications and all but one remains free of disease twenty-four months post-treatment. Adjuvant intraoperative PDT may improve cure rates of recurrent head and neck malignancies by providing for larger tumor-free margins of resection while preserving normal structures.

Photodynamic therapy (PDT) is an innovative treatment involving the use of light-sensitive drugs to selectively identify and destroy diseased cells. Therefore, photodynamic therapy has the potential to treat and cure precancerous and early cancerous lesions (carcinoma in situ (CIS), T1 and T2) of the larynx while preserving normal tissue. Twenty-four patients with recurrent leukoplakia and carcinomas of the larynx were treated with PDT with follow-up to 60 months. Fourteen patients with T1 squamous cell carcinomas of the vocal cord, 2 patients with a T2 squamous cell carcinoma of the vocal cord failing radiotherapy, and 6 patients with CIS and sever atypia were treated with PDT and obtained a complete response and are disease free. One patient with a T3 carcinoma of the larynx was treated with PDT but died 5 weeks post-treatment of unrelated causes and could not be assessed. Photodynamic therapy is a promising therapy for treatment of precancerous and cancerous lesions of the larynx. This therapy may be particularly beneficial for the treatment of recurrent carcinomas of the larynx that have failed conventional radiotherapy, thereby preserving voice and eliminating the need for destructive laryngeal surgery.

We made an experimental and clinical researches to examine Intraoperative Photodynamic Therapy (IPT) as a method to prevent the recidives of tumors. In experimental researches on models with radio-inducated fibrosarcomas and Erlich carcinomas of mice the best method of IPT was worked out. The therapeutic effect was studied also on patients with laryngeal cancer. In researches on C3H mice the antirecidive effect of IPT established with local administration of methylene blue and Ar-laser. We found that IPT (He-Ne laser combined with methylene blue administration) was endured by patients with laryngeal cancers without problems. We got good results of treatment 42 patients with laryngeal cancers with middle localization during three years with using IPT method. This can show the perspectives of using this method in treatment of other ENT-oncological diseases.

A laser doppler vibrometer was used to measure the motion of a simple middle ear model and tympanic membrane vibrations of human temporal bone specimen. Different pathological conditions were simulated: Increasing or decreasing middle ear pressure to defined levels create a situation similar to a barootitis. Additionally the middle ear cavities were partially or totally filled with fluids of different viscosities. Characteristic changes of the vibration patterns were detected: With increasing pressure difference between middle ear and atmosphere the vibration amplitudes decreased. In middle ear effusions diminished amplitudes were obtained, depending on the fluid-occupied volume within the tympanic cavity. The vibration pattern was not influenced by differences in the viscosity of the effusion. Therefore a preoperative examination of a patient with middle ear effusions by laser doppler vibrometer offers no predictive aspect to the decision whether a ventilation tube should be inserted or not.

CO₂ (10.6 micrometers ), Argon (514 nm), and KTP (Nd:YAG) (532 nm) are the lasers of choice for the stapedotomy operation. While each of these lasers is effective in surgically treating otosclerosis, few studies exist which compare the relative deleterious effects of these lasers in a model that is relevant to clinical practice and also based on the physics of laser- tissue interactions. This study focuses on surface temperature changes that occur in otic capsule, cortical, and lamellar bone when treated with clinical laser energy densities. Fresh porcine otic capsule, cortical, and lamellar bone were micromachined to a uniform thickness of 0.8 mm. A microspot manipulator was used for CO₂, testing both continuous wave (CW) and super-pulse (SP) modes. A focused lens based system was used for argon, and a micro fiber was used for KTP. A Hg-Cd-Te infrared imaging system was used to measure temperature. Hot spot temperatures were recorded, as well as the full width-half maximum of the thermal disturbance at that time. The time for the hot spot to return to ambient temperature was also recorded. With visible wavelengths, the experiments were performed in the presence and absence of an initiator (black ink). Temperature elevations with CW CO₂ were markedly elevated relative to SP mode. The CW irradiated tissue also required longer to cool. In both KTP and argon treated bone, minimal surface temperature elevation was recorded in the absence of an initiator. No surface modification was observed by light microscopy. In contrast, the addition of an initiator resulted in marked temperature elevations and significant surface carbonization with these visible wavelengths. The mechanisms of ablation and thermal conduction are discussed along with the clinical relevance of these findings.

Myringotomy--a procedure in which a perforation is made in the tympanic membrane (TM) is performed to gain access to the middle ear for diagnostic or therapeutic reasons. Some medical conditions, especially middle ear infections require an opening that remains patent for weeks or even months. A conventional myringotomy usually closes in a few days which is insufficient time for an underlying disease to resolve. There have been studies reporting modest closure delays of myringotomies done by CO₂ laser from the beginning of 1980's and the procedure has not gained popularity in clinical practice. Many of the mechanisms affecting TM healing delays remain unknown. In an animal model we investigated the closure rates of TM perforations after different types of myringotomies. The animals formed three experimental groups: (1) both ears had a semicircular myringotomy produced either with a knife or with a CO₂ laser; (2) both ears had a round laser myringotomy (1.2 mm in diameter) produced either in a single shot or by a series of small overlapping shots; (3) both ears had laser myringotomy either kidney shaped (1.2 X 2 mm) or round (1.2 mm in diameter) produced by a series of small shots. All myringotomies closed within 42 days without complications. The mean patency of knife myringotomies was significantly shorter (9.8 days) than that of similar laser myringotomies (19.5 days). The mode of laser delivery did not have an effect on the closure rate. Kidney shaped CO₂ laser myringotomies stayed patent significantly longer (mean 25.8 days) than circular (mean 11.4 days). The patency of smaller semicircular laser myringotomies was significantly longer than that of larger circular. The results indicate that certain geometries as well as use of the CO₂ laser delays the closure of myringotomy. When myringotomy is performed for therapeutic reasons not only the size but also the shape should be considered as a factor for extending its length of patency. In the future CO₂ laser may become an instrument for creating reliable myringotomies of different shapes and sizes.

Holmium:YAG (2.1 micrometers ) and Erbium:YAG (2.9 micrometers ) lasers have been suggested for use in neurotologic operations. The relatively high absorption in biologic tissues and minimal thermal diffusion associated with pulsed lasers make them attractive alternatives to CO₂ and visible wavelength lasers, which currently enjoy widespread clinical use. There has been no systematic investigation of the properties of these lasers in a tissue model relevant to temporal bone operations, though there are numerous clinically oriented studies using these wavelengths. The microarchitecture of otic capsule (bone tissue of the inner ear) differs dramatically from bone found elsewhere in the body. Porcine otic capsule was machined into 0.8 mm thick specimens. The ablation rates of Ho:YAG and Erbium:YAG lasers were determined with incident flux varying from 6 - 20 J/cm²/pulse at 4 Hz PPR. Otic capsule specimens were ablated under both wet (physiologic) and dry (chemical dehydration) conditions. With Ho:YAG irradiation, dry otic capsule ablated with multiple episodes of stalling out. The relative number of specimens where stalling out occurred decreased with increasing laser flux. Wet tissue demonstrated similar characteristics, but with a lower ablation rate for a given fluence. In Erbium:YAG treated tissue, similar observations were noted, but the dependence on fluence is less clear in both wet and dry tissues. Water is shown to play a key role in the ablation process. The threshold of ablation is lower in wet tissue than in dehydrated tissue. The homogeneous microarchitecture of otic tissue also strongly influences the ablation process. Possible mechanisms are discussed.

Correction of cartilaginous defects in the head and neck area remains a challenge for the surgeon. This study investigated a new technique for laser-assisted cartilage reshaping. The pulsed 1.44 micrometers Nd:YAG laser was used in vitro and in vivo experiments to irradiate cartilage to change it's shape without carbonization or vaporization of tissue. Two watts of average power in non contact manner was used to irradiate and reshape the cartilage. The extracted reshaped cartilage specimens underwent testing of elastic force with a computer assisted measurement system that recorded the changes in elastic force in the specimens from 1 hr to 11 days post-irradiation. An animal model of defective tracheal cartilage (collapsed tracheal wall) was created, allowed to heal for 6 weeks and then corrected endoscopically with the laser-assisted technique. The results of the in vitro and in vivo investigations demonstrated that it was possible to alter the cartilage and that cartilage would retain its new shape. The clinical significance of the technique is evident and warrants further animal studies and clinical trials.

The protection of endotracheal tubes against laser induced ignition is necessary to enable a safe laser surgery of the upper aerodigestive tract. It was found, that tubes of polymers, like PVC, have a low ignition threshold and even worse evaporate toxic gases when accidentally irradiated by the laser beam. So far, a pure metal tube was described as the safest endotracheal tube. A new compound endotracheal tube build up by a rubber tube surrounded by an ondulated silver foil and a layer of white Merocel^TM-foam, was tested to it's laser stability against the CO₂-laser. The damage threshold of this tube was 3 X 10⁶ W/cm² and is significantly higher than the damage threshold of the metal tube and far above the power density used for coagulation or ablation of tissue. Beside these experimental results, the contribution contains experiences and preliminary results obtained from a randomized clinical study, in which the new compound tube so far has proven to be ideal in handling and till now has not caused any problems concerning the laser resistance.

The usual treatment of snoring in the absence of sleep apneas has been UPPP. Patients are often reluctant to undergo this painful procedure under general anesthesia. The Laser Assisted Uvulopalatoplasty (LAUP) is a new procedure, introduced six years ago by the author, using local anesthesia for the treatment of snoring in an office setting. This technique is designed to correct breathing abnormalities during sleep, caused by pharyngeal airway obstruction in patients suffering of Snoring or Obstructive Sleep Apnea Syndrome. This is done by reducing the amount of tissue in the uvula, the velum, and the upper part of the posterior pillars. LAUP allows surgery for the relief of snoring to be performed in the office, under local anesthesia. LAUP has many advantages over the traditional UPPP. It is simple, reliable, hemostatic, and less painful. It is also less expensive as it can be performed as an outpatient. This makes the LAUP more accessible to patients. Our experience with LAUP in 856 patients from December 1988 to July 1994 (141 women and 715 men) is described. Good results were obtained in 94.8% of patients and there were no complications. This new technique can be easily performed by other otolaryngologists after serious suitable training. LAUP provides a simple alternative for many patients who do not wish to undergo a traditional UPPP.

We present two different methods to treat hypertrophic turbinates in an office environment: (a) with the aid of 1 mm thin hollow waveguides transmitting a CO₂ laser beam to produce char-free ablation of turbinate mucosa, and (b) with the aid of a 800 micron thin optical fiber transmitting low power Nd:YAG laser radiation to interstitially coagulate and shrink submucosal tissue. Char-free ablation of mucusal tissue: An office CO₂ laser regularly used for LAUP in the treatment of snoring problems is operated in the Superpulse mode (peak power 350 W) at 8 W average power. The optical beam is coupled to angled and straight hollow waveguides. Ablation of inferior turbinates is performed within a few minutes under topical or local anesthesia. No post operative packing is required and the patient can return to normal activities. Healing is fast due to the highly controlled superficial thermal damage. Interstitial coagulation of inferior turbinates: Submucosal coagulation of tissue is attained with a flat 800 (mu) fiber longitudinally pushed and pulled while operating an Nd:YAG laser at 8 W power level. A 4 - 6 mm thin coagulated and shrunken volume of cylindrical shape is being produced with no damage to bones or mucosa. The procedure is fast and performed under local anesthesia. An analysis of both surgical techniques and clinical results with over 100 patients will be presented.

The pharyngeal airway obstruction during sleep in the Obstructive Sleep Apnea Syndrome (OSAS) can be improved after treatment by LAUP (Laser Assisted Uvulopalatoplasty). This new technique, performed under local anesthesia, permits the snoring treatment without any hospitalization, or general anesthetic; like an ordinary dental visit. This is done by reducing the amount of tissue in the uvula, the velum, and the upper part of the posterior pillars. Our experience with the LAUP in Sleep Apnea Syndrome is described, from December 1988 to May 1994, in 70 patients. Among 62 patients classified as successful `responders', the respiratory disturbance index was reduced more than 50%. Among all the 70 patients: in 51.4 % of cases (36 patients), there's a healing of snoring and Sleep Apnea Syndrome. In 37.2% of cases (26 patients), there's an improvement reduction of length and number of apneas and a significant improvement in nocturnal oxygen saturation. 11.4% (8 patients), are relative failures, with always decrease of snoring, but still Sleep Apnea Syndrome, (with a higher B.M.I.). There were no important complications reported. Patients withstand it well and there's had a better tolerance of the C.P.A.P. in the cases of OSAS LRPP failures. Popularization of LAUP will require serious training of surgeon and further long-term studies.

Vascular ectasias (dilatation) and vascular lesions of the larynx are difficult to treat with exciting modalities. Varix (enlarged vessel) of the vocal folds, vocal fold hemorrhage, vascular polyp, hemangioma, intubation or contact granuloma are common problems which disturb voice. Current applications of CO₂ laser and cautery often damage the delicate vocal fold cover. The 585 nm dermatologic pulsed dye laser may be an ideal substitute. Two adult canines were examined under anesthesia via microlaryngoscopy technique. Pulsed dye laser (SPTL-1a, Candela Laser Corp., Wayland, MA) energy was delivered via the micromanipulator with the 3.1-mm spot size in single pulses of 6, 8, and 10 Joules/cm² and applied to the vessels of the vocal folds, epiglottis, and arytenoid cartilage. Endoscopic examination was carried out immediately after the treatment and at 4 weeks postoperatively. The animals were sacrificed at 3 weeks, larynges excised, and whole organ laryngeal section were prepared for histology. Pulsed dye laser thrombosed vessels of the vocal fold using 6 or 8 Joules/cm². Vascular break and leakage occurred at 10 Joules/cm². Follow up examination showed excellent vessel obliteration or thrombosis without scarring or injury to the overlying tissues. Histologic examination shows vascular thrombosis without inflammation and fibrosis in the vocal fold cover. Pulsed dye laser may have promise in treatment of vascular lesions of the larynx and upper airway.

68 cases of glottic carcinomas (T1 53 and T2 15 cases) treated with CO₂ laser or KTP/532 laser April 1982 through March 1992 were reviewed. The patients were followed up from 13 to 130 months (mean 60 months). The 3-year determinate survival rate was 100% and 5-year determinate survival rate was 100% for T1 and 80% for T2. The voice conservation rate was 97% for T1a, 83% for T1b, and 80% for T2 and vocal function was satisfactorily preserved for daily life. The results led to the following conclusions: (1) Glottic T1 carcinomas can be treated by laser surgery alone. (2) Lesions involving the anterior commissure can be treated by laser excision and vaporization. (3) Laser surgery followed by external radiation therapy for glottic T2 carcinomas improves the voice conservation rate.

Tonsillectomy is one of the most frequently performed surgeries which is not free from post- operative morbidity. We have developed a non contact photocoagulation technique using 1.06 micrometers Nd:YAG laser and tested its safety and efficacy in an animal model. Eight animals were divided into the laser coagulation group (6 animals) and the laser excision group (2 animals). Tonsils of the laser coagulation animals were irradiated with 8 - 10 W of laser power for 5 - 6 min in a slow painting-like motion over the surface of a tonsil until slight blanching of mucosa was noticed. Tonsils of the laser excision group were resected with 25 - 30 W of 1.06 micrometers Nd:YAG laser power through a contact fiber. The animals were examined endoscopically at 1.5 hrs and at 2, 5, 12, 30, and 42 days post treatment. Atrophic process was followed until total disappearance of tonsillar tissue was observed. The animals were sacrificed at various time intervals and the tonsillar specimens were collected for gross and histological examination. The thermal damage to mucosa and adjacent tissues was minimal which we attribute to a low laser power and cooling from preoperative injection of saline into subcapsular space. The potential advantages of this technique include intact mucosa with no intra- or post-operative bleeding, less pain, and avoidance of general anesthesia. These advantages may enable this surgery to become an in-the-office procedure.

Hyperlipidemic states are associated with focal accumulations in arterial walls of oxidatively modified low density lipoprotein (LDL) and monocyte-derived liquid-laden macrophages, biochemical and cellular hallmarks of atheromatous lesions. Mechanisms underlying the generation and cellular uptake of oxidized LDL are still incompletely understood. We have used laser-induced fluorescence spectroscopy to monitor the formation, intracellular accumulation, and tissue distribution of oxidized LDL. Oxidatively modified LDL excited by a XeCl excimer laser (308 nm) exhibits unique spectral characteristics that distinguish it from native (non-oxidized) LDL. The same spectral characteristics were demonstrated in lipid-rich atheromatous lesions, macrophages after incubation with oxidized LDL, and peripheral blood monocytes from hyperlipidemic, but not normolipidemic subjects. Detection of oxidized LDL in peripheral blood monocytes and arterial tissue may provide information on the atherogenic activity of hyperlipidemic states and serve as a novel risk factor for the assessment of atherosclerosis.

In vitro studies have shown that normal and abnormal human coronary artery segments can be differentiated on the basis of their Raman spectra. A compact near infrared Raman spectroscopy system has been constructed for in vivo measurement of the biochemical composition of human coronary artery. A 500 mW air-cooled diode laser generates 830 nm excitation light which is delivered via a fiber optic probe to the arterial wall. Scattered light is collected by the same optical probe and delivered to a f/1.8 imaging spectrograph, which disperses the light onto a liquid-nitrogen-cooled deep-depletion CCD detector. A spectral model has been developed to quantify the protein, lipid and calcium mineral content in coronary artery wall. Raman spectra with sufficiently high S/N for extracting biochemical information can be collected in less than one second. In vivo studies during open heart surgery are currently being conducted which will establish near infrared Raman techniques as a real- time diagnostic tool.

The purpose of this study was to determine whether the addition of Photodynamic Therapy (PDT) using the photosensitizer Photofrin^* (P^*) following balloon angioplasty (BA) could prevent restenosis in an atherosclerotic animal model. Bilateral iliac atherosclerosis was created in 21 Yucatan miniswine. Six weeks later, P^* 2.5 mg/kg was given IV 24 hours prior to BA (4 mm X 20 mm, 1 inflation). Following BA, swine were randomly allocated to receive PDT via a fiberoptic probe with laser energy or the same probe without laser energy. The fiberoptic probe had a 1 cm cylindrical diffusing tip and was passed co-axially through a custom catheter to ensure central location of the probe. A continuous wave argon ion-pumped dye laser tuned to 630 nm was used to provide a fluence of 100 J/cm². Four weeks later, swine were sacrificed and vessels perfusion-fixed in-situ with glutaraldehyde and analyzed by ocular micrometry. Five occlusions occurred, all in the PDT + BA group. Percentage intimal thickness (mean +/- SD) was 51.0 +/- 29.5 in the BA group and 71.2 +/- 35.2 in the BA + PDT group (p equals 0.21). These results suggest that the addition of PDT following BA does not prevent restenosis.

Photodynamic therapy (PDT) has been proposed as a treatment for intimal hyperplasia (IH). We studied the effect of PDT on the development of IH following endothelial injury, using the photosensitizer Metatetrahydroxyphenyl-chlorin (m-THPC) and 652 nm illumination. 9 mini- pigs were used in 3 groups of 3. Pigs in the first group (balloon alone; BA) were anaesthetized and the lower 4 cm of abdominal aorta was denuded using a balloon catheter through the right femoral artery. In the second group (light alone; LA) the procedure was repeated, followed by illumination of the denuded area at an energy density of 20 Jcm^-2 using a transparent PDT catheter. In the third group pigs were sensitized and an intravenous injection of 0.3 mg/kg of m-THPC 4 hours prior to balloon injury and illumination (PDT Group). Animals were allowed to recover for 8 weeks before being killed and perfusion fixed with 10% formal saline. 5 sections were cut from the treated segments and stained for elastin. Specimens were measured by a computerized morphometry system and the areas of the lumen (L), intima (I) and media (M) were measured. The degree of intimal hyperplasia was expressed as (a) I/M; (b) I/(I+M) and (c) I/(I+L) to take account of changes that could have occurred to the media and the overall diameter of the vessel. We found that when compared to BA controls, the lumenal area was decreased by 46% in LA group and increased by 44% in PDT group. The changes in the medical areas were minimal. These results show that both light alone and PDT produced more intimal hyperplasia than balloon injury alone (P < 0.002 for both groups, Student's t test). When allowance is made for the large increase in lumenal area associated with PDT the degree of intimal hyperplasia I/(I+L) was significantly reduced in PDT treated vessels when compared to those treated with light and balloon alone in spite of the greater absolute area of the intima in the PDT group. We conclude that PDT under the above conditions not only failed to prevent IH, but was associated with a significant increase of intimal area. The increase in the dimensions of the PDT treated vessels reduced the detrimental effect of IH and improved the overall diameter of the lumen.

The long-term benefit of coronary or peripheral vascular interventions is limited by restenosis, due to intimal hyperplasia (IH). Photodynamic therapy (PDT) with systematic delivery of the photosensitizing drug, performed either at the time or shortly after vascular injury, has been demonstrated to effectively inhibit the development of experimental IH. However, in order to deliver large quantities of the photosensitizer, but avoid systematic photosensitization, local delivery of the drug appears to be an advantageous option. An experimental model was therefore developed to deliver benzporphyrin derivative (BPD-MA) directly into isolated segments of balloon-injured rat common carotid arteries, and to study the uptake in serum and arterial tissue by means of spectrofluorometry. Furthermore, early effects of local versus systematic drug delivery and subsequent PDT treatment, were investigated with light microscopy and morphometric analysis. Local delivery of BPD lead to effective drug concentrations in the artery with complete depletion of endothelial and smooth muscle cells, already 24 h after PDT. The media appeared compacted and acellular. No thrombosis or occlusion were observed. Serum concentrations of BPD, after local delivery, were at the detection threshold, whereas systematic application resulted in significantly higher serum but equivalent tissue drug concentrations. In conclusion, these data demonstrate that local delivery of BPD results in tissue concentrations, appropriate to perform an efficient vascular PDT treatment of the arterial wall.

Tin ethyl etiopurpurin, SnET2, is presently undergoing clinical trials for the treatment of cutaneous cancers and AIDS related Kaposi's sarcoma. Extensive pre-clinical work has been performed investigating the uptake, localization, and retention of SnET2 in catheter induced atheromatous plaques in New Zealand White (NZW) rabbits and juvenile female swine. The ultimate goal is to employ SnET2 for the prevention of intimal hyperplasia following various forms of angioplasty, thus enabling the prevention of a significant cause of restenosis. To that end, a dose/response study was undertaken to investigate the effect of varying total light dose (200, 100, and 50 J/cm²) and light dose rate (637, 318, 159 mW/cm²) during SnET2-Photodynamic Therapy, SnET2-PDT, of catheter induced plaque in a NZW rabbit iliac artery model. The SnET2 dose was held constant at 1.0 mg/kg b.w. and light was delivered intraluminally via a guidewire compatible light diffusing balloon catheter. The greatest light dose of those tested without inducing thermal damage was found to be 318 mW/cm² while the total light dose of 50 J/cm² produced PDT effect which was limited to the neo-intima. A relatively substantial total light dose of 200 J/cm² was shown to produce a transmural PDT effect. This study demonstrated that the depth of PDT effect can be modulated by varying the total light dose.

One significant avenue for cost containment in medical care is the application of affordable spin-off technology. Innovative methods for the efficient prevention and treatment of atherosclerotic plaques in cardiac arteries will have significant implications for reducing health care costs in a large patient population. We report on preliminary work aimed at exploiting advanced sensing, fiber optic and materials technologies to create an innovative medical instrument: the Ultrathin Angioscopic Guidewire (UAG). The UAG uses an innovative method to combine high resolution fiber optic imaging bundles with flexible guidewire extensions into a integral unit having a diameter of less than 350 microns. The UAG would serve as the guidewire over a integral unit having a diameter of less than 350 microns. The UAG would serve as the guidewire over which the treatment catheter would ride eliminating repeated removal and reinsertion of the catheter for evaluation. The resulting images are coupled to a high resolution, image intensified detector. Use of digital image capture before and after treatment combined with frame processing allows for a quantitative evaluation of lesion removal and archival data to establish treatment efficacy. Once developed, this instrument will be particularly useful in conjunction with current interventional procedures. As a diagnostic tool, the intensifier in the UAG allows for sensitive imaging for application to in vivo bio/chemiluminescent immunoassays. We will present design details and discuss proof of principle results with the first prototype UAG.

A novel radiofrequency ablative system (40 msec-train pulses with twenty 200 msec pulses at the carrier frequency of 750 KHz and 1 Hz repetition rate) aimed at recanalizing totally occluded peripheral arteries was investigated by means of in vitro tissue ablation from human postmortem arterial wall samples. The samples were submitted to irradiation with a guidewire 150 cm long, maximum diameter of ceramic tip 0.033 inch positioned perpendicular to the tissue surface in saline, contrast medium or blood using varying generator power. Ablation efficacy was determined as the depth of vaporization per pulse delivered. Electrical current for the train duration was measured as voltage at the 1 ohm-resistor. In saline, the ablation efficacy increased from 8 to 65 mm/pulse with generator power increasing from 11 W to 27.5 W. There was no significant difference in the ablation efficacy between saline and blood. In contrast medium, the ablation efficacy was significantly lower. For the same generator power, the electrical current varied during the ablation procedure from 1.3 +/- 0.2 A at the beginning of the procedure to 1.1 +/- 0.2 A after the first pulses and to 2.0 A before artery wall perforation occurred. Neither tissue ablation nor current variations were observed when radiofrequency energy was emitted on calcified tissue. The diameter of craters was 0.89 +/- 0.1 mm (range: 0.85 - 0.96 mm). No major thermal injury such as carbonization or charring was observed. Thus, (1) radiofrequency energy emitted through a guidewire is reliable and effective for the ablation of arterial tissue; (2) the depth of penetration is related to the generator power; (3) the ablation efficacy is greater in saline and blood than in contrast medium; (4) the system is not effective in highly calcified tissue; (5) the procedure may be monitored by electrical current measurements.

A pulsatile blood flow model was used to estimate the influence of position of Doppler guide wires with 12 MHz forward looking ultrasound transducers on the average spectral peak velocity. Three 0.014-inch and three 0.018-inch Doppler guide wires were positioned in plastic tubes ranging from 1.7 mm to 8.0 mm internal diameter. Blood flow of 50, 100 and 200 ml/min was adjusted using a roller-pump. The flow velocity was lower by 54% near the wall than in the center of large tubes (diameter 8.0 mm). In tubes of 2.9 mm and 4.2 mm in diameter the maximum variations were 11% and 22.5% for the 0.014-inch guide wire and 7.5% and 20% for the 0.018-inch guide wire, respectively. No variance in velocity related to wire position was observed in small (1.7 mm) tubes. The system was not sensitive to angular displacement of the guide wire in the range of +/- 30 degree(s). These results demonstrate that intravascular Doppler ultrasound flowmeter may be accurately utilized for measurements of blood flow velocity in small coronary arteries without any need to reposition the guidewire.

Hemopump is a ventricular assist device which is aimed at improving the management of high- risk patients for PTCA. The aim of the study was to access coronary blood flow velocity during hemopump. The hemopump was inserted percutaneously into the femoral artery. Coronary blood flow was measured with a 12 MHz Doppler-tipped guidewire proximal and distal to the stenosis before, during and after PTCA. Coronary vascular reserve was assessed by intracoronary 12 mg bolus injection of Papaverine. Collateral flow was assessed during balloon occlusion by inverted velocity signals below baseline. Eight patients aged 59 +/- 11 yrs, with unstable angina, a last patent vessel and/or major left ventricular dysfunction (EF < 0.20) had hemopump during PTCA of stenosis (86 +/- 14%) of the LAD (n equals 4) or the LCX (n equals 4). Collateral flow was slightly increased (+25 +/- 18%) by the Hemopump. Hemopump did not strongly affect coronary flow velocity, did not significantly increase collateral flow and increased slightly coronary vascular reserve.

We performed simultaneous angioscopy and intravascular ultrasound imaging (IVUS) to evaluate the luminal changes of cardiac chambers, valves and vessels in patients with various categories of cardiovascular disease. We observed cardiac chambers in 7, coronary arteries in 3, aortic valve in 6, aorta in 10, vena cava in 2, pulmonary arteries in 3 and femoral arteries in 5 pts. The angioscopy was suitable for detection of the changes in color and for 3D evaluation of small changes. The IVUS was suitable for detection of calcified tissues and for evaluation of cardiac and vessel wall structures. Furthermore, we could observe dynamic motion of the cardiac valves by the IVUS. The results indicate that simultaneous observation by IVUS and angioscopy gives us much more information on the cardiovascular changes.

Techniques are being developed to `tack weld' broken bones together with the help of a laser. These techniques would, in some instances, allow doctors to avoid the use of foreign fixation devices such as metal plates and pins for the repair of small bones as in the delicate maxillofacial and nasal bones. Successful laser `welding' of chicken tibias in vitro was reported by the authors last year. Since that time, parameters affecting the strength of the weld have been examined. Several different compositions have been tested as possible `solders' for the welding process. These include substances such as reagent grade gelatin and a hydroxyapatite-based cement. The bones welded with the gelatin mix and subsequently refrigerated have been consistently stronger than those welded without gelatin. The hydroxyapatite-based cement did not increase weld strength. The effect of the concentration of a demineralization solution, hydrochloric acid, has also been examined. Lower pH values correspond to stronger welds. The tensile strength of the weld has also been shown to depend on the extent of hydration during the 24 hours after laser welding.

Because indocyanine green (ICG) dye is being used in tissue soldering, investigation of its degradation properties has become important. Studies have demonstrated the kinetics of indocyanine green degradation on light exposure. Temperature dependent changes have not been characterized. Since tissue soldering is a thermal process, we examined how absorption characteristics of aqueous ICG solutions change after heating. A 3.23 mM ICG stock solution in 2.5% human serum albumin (HSA) was prepared daily. From the stock solution, 1.5 ml samples were light shielded and heated to 100 degree(s)C for intervals of up to 5.5 hours. Control samples were maintained at room temperature. After heating, samples were diluted to 16.6 (mu) M ICG with 2.5% HSA for scanning. Absorbance from 200 to 900 nm was measured using an absorbance spectrophotometer. Peak absorption intensity decreased as heating time of samples increased from 1 to 5 hours, with the first consistently detectable change occurring after 1 hour. Absorption peak was stable at 805 - 808 nm with no novel peaks and absorbance magnitude was reduced only 2% over 1 hour. Lower temperatures more commonly seen in laser welding (60 - 80 degree(s)C) produced even smaller reductions in absorption intensity. Measurable thermal degradation of aqueous ICG solutions occurs at 100 degree(s)C after a period of hours. Therefore, thermal degradation of ICG in the context of tissue soldering is probably insignificant.

Photothermal coagulation of indocyanine/fibrinogen/hyaluronate `glue' with diode laser irradiation (ICG) produces mechanically more stable wound closures in rat skin incisions when compared to wounds closed by CW HoYAG laser irradiation alone. However, neither laser- medicated technique produced wound closures as stabile as the sutured wounds. The predominant advantages of photothermal closure of skin wounds are short operating times and formation of fluid tight bonds with minimal tissue manipulation. The added stability of ICG/laser closed wounds demonstrated in this study suggests the possible usefulness of this technique to close skin wounds in areas of low skin tension.

Best outcome in nerve repair requires precise alignment and minimization of scar at the repair interface. Surgeons attempt to create the sharpest cut surface at the nerve edge prior to approximation. Pulsed laser modalities are being investigated in several medical applications which require precise atraumatic cutting. We compared nerve trimming with the Er:YAG laser (1375 J/cm²) to conventional steel knife trimming prior to neurorrhaphy. Sprague- Dawley rats were anesthetized with ketamine and xylazine. Under operating microscope magnification the sciatic nerve was dissected and transected using one of the test techniques. In the laser group, the pulses were directed axially across the nerve using a stage which fixed laser fiber/nerve distance and orientation. Specimens were sent for scanning electron microscopy (SEM) at time zero. Epineurial repairs were performed with 10 - 0 nylon simple interrupted sutures. At intervals to 90 days, specimens were harvested and sectioned longitudinally and axially for histologic examination. Time zero SEM revealed clean cuts in both groups but individual axons were clearly visible in all laser specimens. Small pits were also visible on the cut surface of laser treated nerves. No significant differences in nerve morphology were seen during healing. Further studies to quantify axon counts, and functional outcome will be needed to assess this technique of nerve trimming. Delivery system improvements will also be required, to make the technique clinically practical.

The purpose of this study was to evaluate the efficacy, histology, and strength of laser welding in repair of sharply transected rat Achilles tendons. In 26 adult, male Sprague-Dawley rats, the severed tendons were repaired with a 7-0 nylon, modified Kessler core suture followed by either a running 9-0 nylon epitendinous suture or a circumferential CO₂ laser epidendinous weld using 25% human albumin as a solder. All repairs were timed and post- operative tensile strength was analyzed with material testing equipment. In addition, histologic testing was performed on both types of repairs. The mean time to complete the epitendinous repair in the laser group was 3.5 minutes and in the suture group, 8 minutes. The mean ultimate tensile strength in 6 normal tendons was 40.9 Newtons (N) with group standard deviation of 5.2 N. When compared with normal controls, post-operatively both types of tendon repairs resulted in tensile failure at lower forces. The ultimate tensile strength for the epitendinous suture repair and the laser welds were 13% and 6% of normal controls, respectively. Twenty tendons with epidendinous suture repair had mean ultimate tensile strength of 5.4 (+/- 1.2) N, while the 17 tendons with laser wends failed at 2.6 (+/- 0.9) N. Histologic evaluation of tendons repaired with CO₂ laser revealed areas of coagulation and edema on the surface of tendon edges. Post-operatively, greater tissue changes were noted in laser treated tendons than those repaired with sutures. Laser welding of epitenon is possible and can be completed faster than the suture repair. The repaired tendon surface appears smoother and less bulky after laser treatment. However, significantly decreased immediate post-operative strength was demonstrated by the use of Kruskal-Wallis one way analysis of variance and Turkey's pairwise comparison.

Laser tissue welding is a sutureless method of wound closure that has been used successfully in nerve, skin, and arterial anastomoses. We welded an elastin-based biomaterial that elicits minimal foreign body reaction to the intimal surface of porcine aorta. The aorta was stained with indocyanine green dye to efficiently absorb the 808 nm diode laser light. Laser welding with a pulsed diode laser thermally confines heating to stained portion of tissue, minimizing adjacent tissue damage. Laser welds of stained aorta to biomaterial were attempted by sandwiching the samples between glass slides and applying pressure ranging from 4 - 20 N/cm² for 5 ms pulse durations and 83 mJ/mm² radiant exposure. Welds were successful for pressure above 5 N/cm². Transmission measurements of stained aorta were made using radiant exposures of 6 - 129 mJ/mm² using pulse durations of 0.5 - 5 ms. Transmission increases and reaches a maximum of 80 - 85% with successive pulses for radiant exposure greater than 26 mJ/mm² for a spot size of 9 mm² and 13 mJ/mm² for a spot size of 36 mm².

Laser welding has been used for connecting various tissues in the body. In urology such welding has the advantage of forming an immediate water tight seal. We have developed a fiberoptic system that makes it possible to monitor and control the temperature of the tissue during welding. In previous work we demonstrated that this system could be successfully used to weld punctures in the urinary bladder of rats. It was found that optimal welding was obtained at a temperature of 55 degree(s)C. In this work we used the same system for welding of large openings (cystotomy) in the urinary bladder of rats. In early experiments we used stay sutures and decompressing catheters. It was later found that complete closure can be obtained with CO₂-laser welding alone. This work demonstrates the feasibility of using temperature controlled laser welding as an efficient surgical tool.

The results of a closed loop thermal feedback controlled laser-assisted tissue welding study in vivo are reported. A series of experiments was carried out to study and compare the weld strength and healing response of sutured and laser welded rat enterotomies with and without temperature feedback control (TFC) using a cryogenically cooled Ho:YAG laser. Although assignment of animals to three groups (control sutured, laser welded with and without TFC) and four observation periods (1, 3, 7, and 21 days) was randomized, several laser welded enterotomies without TFC had complications resulting in death of the animals. Those experiments were repeated. From the failure rates encountered, it is shown that TFC improves the quality of laser-assisted enterotomy closures.

Skin cancer is the most frequently occurring cancer of all cancers. Each yea rover 500,000 new cases of skin cancer will be detected. A high percentage of skin cancers are diseases in which fatalities can be all but eliminated and morbidity reduced if detected early and treated properly. These skin lesions are distinguished generally by subjective visual inspection and their definitive diagnosis requires time-consuming expensive histopathological evaluation of excisional or incisional biopsies. In vivo experimental evidence published in the literature has shown that cancerous skin lesions have different total diffuse reflectance spectra than non- cancerous lesions or normal skin. Therefore, cancerous skin lesions may be differentiated from non-cancerous skin lesions by comparing the optical properties of the skin lesions with those of the surrounding normal skin sites, where the optical properties of the normal skin sites are used to account for different types of skin or different areas of skin. We have demonstrated that the effect of melanin concentration on the diffuse reflectance may be removed by extrapolating the reflectance at different wavelengths to an apparent pivot point. Because the concentration of melanin does not indicate malignancy, the removal of its effect is important to avoid false detection. The total diffuse reflectance depends on the albedo and anisotropy of tissues. Therefore, the total diffuse reflectance will remain the same as long as the anisotropy and the ratio between the absorption coefficient and the reduced scattering coefficient remain the same. Separating the absorption and scattering effects should enhance the detection sensitivity of skin cancers.

Various continuous wave lasers have been effectively used for sclerosis of cutaneous vascular lesions. The risk of scarring has been as high as 15% in some applications, however. Pulse dye lasers have virtually eliminated scarring as a complication, substituting high cost and cumbersome operation. Pre-clinical studies have demonstrated the ability of the 810 nm gallium-aluminum-arsenide diode laser in photosclerosis. In this study, a small group of patients (n equals 6) were treated with a pulsed 810 nm diode laser (Surgimedics, The Woodlands, TX). Pulse widths used were 5 - 15 msec with corresponding energy densities during the square wave pulse of 14 - 42 J/cm². Pulse interval was 32 msec. Lesions treated include telangiectasias (n equals 5), spider veins, (n equals 4), capillary dermal malformation (n equals 1) and a cutaneous venous malformation (n equals 1). Lower extremity spider veins were the most resistent to treatment, rarely disappearing entirely. Telangiectasias were most responsive, usually disappearing after one treatment. No scarring was noted and textural changes were seen in only one patient. While these data are preliminary and parameters have not been optimized, pulsed diode laser exposure can be an effective treatment for cutaneous vascular lesions.

Although the direct measurement of in-vivo stratum corneum hydration is relatively straightforward using the technique of opto-thermal transient emission radiometry, assessing the effect of a topically applied substance can be complex. The substance itself may change over time and may also contribute to the measured opto-thermal signal. The method developed to account for these changes uses concurrent in-vivo and in-vitro measurements. It is illustrated with topically applied petroleum jelly, dimethyl sulphoxide (DMSO) and an anti- perspirant. The petroleum jelly caused an increase in stratum corneum hydration, whilst DMSO caused a decrease, which recovers over 90 minutes. The anti-perspirant was applied before exercising and, whilst an untreated site became more hydrated, the treated site was found to become drier.

High powered lasers have been used in dermatological procedures such as tattoo removal. This use is associated with a potential, biological hazard of high speed tissue particles from the laser field. It has been proposed that by applying a clear dermatological would dressing directly over the laser treatment site, it may be possible to completely trap the potentially airborne tissue particles from the procedure. Some important questions must be addressed prior to the implementation of such a technique. While the use of a wound dressing may significantly reduce the airborne materials during the laser procedures, new problems may arise: 1 . The wound dressing or some of its components may absorb excessive amount of light energy. This would result in a very localized temperature rise which may be harmful to the patient; 2. The smooth surface of the wound dressing material could induce specular reflection of the incident laser beam, thus introducing a laser hazard to the staff and patient. To address these possible problems, we studied a series of ClearSite Wound Dressings which have been reportedly tested for such laser procedures. The objective of the studies were, to determine if the use of ClearSite in conjunction with laser procedures poses a possible hazard to either the patient or to the Operating Room personnel, and to determine the effect of the ClearSite dressing on the optical characteristics of the light beam. The latter includes light absorption and transmittance for various wavelengths.

The clinical application of the CO₂ laser for skin surgery has traditionally been plagued with a number of inherent disadvantages. These problems mainly consist of variable depth of penetration, dermal charring with thermal build-up, and a slow surgical technique. This has severely limited the success and usefulness of the laser in aesthetic plastic surgery. An optomechanical flashscanner unit-`Swiftlase<sup>TM</sup>', was coupled to a continuous-wave CO<sub>2</sub> laser and used during numerous plastic surgical procedures--both reconstructive and purely aesthetic. The instrument uses two rotating mirrors to cause a vaporizing laser beam to scan across target biological tissue in a somewhat sinusoidal array, thus modulating the CO<sub>2</sub> laser. Another flashscanner unit, `Silktouch^TM' was also utilized. The scanning pattern of the Silktouch^TM yields a whirling spiral across the target and is typically used in a pulsed mode. Areas that were treated in this study included the face, trunk and extremities. Treatment mainly consisted of management of facial wrinkles and scars, benign lesions, and rhinophyma. Histology confirmed depth of dermal penetration as a function of fluence. There were no wound healing complications. Healing occurred in a predictable manner dependent on depth of laser penetration. Conservative, primarily ablative flashscanning CO₂ laser surgery has usefulness for treatment of patients in aesthetic surgery and offers major advantages.

The use of Q-switched laser has been well documented in the treatment of pigmented lesions, particularly in the tattoo removal. To better understand the ablation process by Q-switched lasers, we carried out an analysis on the states and other physical properties of certain tissue/pigment under the action of a strong transient electric field associated with the high energy nanosecond laser pulses. The dependence of the ablation threshold of transient electric field on the chromophore absorption has been found to be weak. A plasma ablation model is used to interpret previous experimental results. The comparison of the plasma model with the conventional selective photothermolysis model has led to a new design concept of Q-switched lasers for dermatology surgery.

The strong pulsed lasers radiation on the Neodim glass was used for the treatment of 265 patients with stage I skin melanoma. To 230 (86.4%) of them the treatment was carried out 5 years ago and even earlier. The duration of follow-up was from 1 to 22 years. The local recurrence of melanoma was diagnosed in 2 (0.75%) of these patients. Regional metastases developed in 44 (16.6%) patients, distant metastases--in 12 (4.5%) patients; in 1 (0.4%) patient the transport metastasis was revealed. More over, in patients to whom this type of treatment was carried out 5 years ago and even earlier regional metastases were diagnosed in 19.1% of cases, distant metastases--in 5.2% of cases, and transport metastases--in 0.4% of cases. 5-year survival rate of the patients made up 83.2%. In case of the I level of invasion (according to Clark classification) 100% of patients were alive for 5 years and even longer, in case of the II level of invasion this index made up 92.3%, in case of the III level--85.7%, and in case of the IV level--80.5%. In melanomas the thickness of which did not exceed 1.5 mm (according to Breslow classification) 5-year survival rate of the patients made up 96.7%, and in the tumors being from 1.51 mm to 4.5 mm thick this index mae up 80.0%. The strong pulsed lasers radiation is the effective method of treatment of plane or slightly elevated skin melanomas of the I-IV levels of invasion (Clark classification) the thickness of which is up to 4.5 mm according to Breslow.

The objective of this study was to compare the antibacterial effects of selective laser treatments on contaminated wounds. Comparisons were made using the diode (808 nm) laser with and without an accompanying chromophore, Nd:YAG (1064 nm), and KTP (532 nm) lasers. A known quantity (mean concentration of 7.9 +/- 1.9 CFU/ml X 10⁸) of bacterial organisms (Staphylococcus intermedius) was inoculated into skin incisions aseptically made on the backs of experimental rabbits. The bacteria were allowed to adhere/colonize for one hour, and each site was then treated with various laser modalities. Tissue samples were taken at one and forty-eight hours after treatment. The number of viable bacteria was then quantitated (CFU/ml) by a spot-plate counting technique. Initial results illustrated the fact that selective photothermolysis of superficial cellular layers of targeted tissue occurred with an accompanying decrease of bacterial numbers that virtually created a `clean' (organisms numbers less than 10⁵ per gram of tissue) wound. This effect was especially noticeable using the diode laser (808 nm) and an accompanying chromophore, indocyanine green.

Conventional radical prostatectomy in the dog has historically been attended by unacceptably high incidence of urinary incontinence (80 - 100%). Ablation of the prostate can be accomplished in the dog by transurethral irradiation of the prostate with the Nd:YAG laser and a laterally deflecting fiber. Exposure has ranged between 40 and 60 watts for 60 seconds at 4 fixed locations. Although prostatectomies performed with the above described technique offers significant advantage over conventional prostatectomies, the high power density at each location can result in small submucosal explosions (`popcorn effect') that increase the potential for bleeding and rupture of the prostatic capsule. We describe a new technique in which the energy is applied continuously by a laser fiber rotating around a central point. Delivering 40 watts of Nd:YAG energy for 4 minutes using a new angle-delivery device (Urotek<sup>TM</sup>), we produced results comparable to those of other previously reported techniques in the canine model with two added advantages: (1) a more even application of heat resulting in no `popcorn' effect and (2) a more reliably predictable area of coagulative necrosis within a given axial plane. This technique should provide additional safety for the veterinary surgeon performing visual laser ablation of the prostate in the dog.

Thirty-five clinical cases received laser disc ablation utilizing a uniplanar fluoroscopically guided percutaneous technique over a three year period. With the dog in right lateral recumbency, uniplanar fluoroscopy was utilized to guide the placement of 20-gauge, 2.5 inch spinal needles percutaneously through the left epaxial soft tissues into the nucleus pulposus with the dog in right lateral recumbency. The needle was advanced in increments following palpation and brief fluoroscopic observations to insure avoidance of the spinal cord and other vital structures. Entrance into the intervertebral disc was identified by a characteristic `gritty' feel of the needle passing through the annulus fibrosus. The dog was then placed in sternal recumbency, and the needles adjusted to place the tip approximately one-third of the distance into the disc. The laser fiber was then placed through the needle into the nucleus pulposus to ablate the nucleus with holmium laser energy. No detrimental side effects of this technique have been identified with the exception of one case. This single exception suggests that this procedure should not be performed on dogs with acute disc herniation. The technique appears safe given adherence to careful placement of the spinal needles and proper clinical criteria for patient selection.

Pyropheophorbide-a-hexyl ether (HPPH) is a new photosensitizer for use with photodynamic therapy (PDT) that has shown promise in laboratory animals. PDT, using this drug, is being used to treat canine patients afflicted with hemangiopericytoma and oral squamous cell carcinoma (SCC) at the University of Missouri-Columbia College of Veterinary Medicine. To date, 11 dogs with hemangiopericytoma and 5 dogs with oral SCC have been treated using a combination of surgery and PDT. Thus far, there have been no serious complications attributable to the treatment. Two dogs have had recurrences of the hemangiopericytoma and there have been no recurrences of SCC with a median follow time of 5 months. Both recurrent hemangiopericytomas were in patients with large tumors that had previous surgery. This study is ongoing and no conclusions have been reached; however several observations are noted. It appears that PDT using HPPH is safe is dogs, and may decrease the recurrence rate of Hemangiopericytomas. In dogs with oral SCC, the treatment is effective is causing necrosis and sloughing of the tumor tissue, and recurrences have not been noted on follow-ups up to 6 months.

Focal thrombosis was induced in the dorsal funiculus of the rat spinal cord by exposing the cord to light following intravenous injection of the photoactive dye, rose bengal. The light source was a 599 standing wave dye laser, pumped by an Innova 70 - 4 argon ion laser (Coherent Ltd, Cambridge, UK) and the light was delivered to the operative site via an optical fiber. The histological characteristics of the development and resolution of the lesion have been studied. Forty rats were examined with light and electron microscopy at various time points between 30 minutes and one month after irradiation and the lesion length was measured. Platelet aggregation, increased extracellular space in the white matter and vacuolation of the neurones and glia of the grey matter were present 30 minutes after injury. Progressive necrosis of the white and grey matter developed over the subsequent 24 hours to produce a fusiform lesion that occupied the dorsal funiculus and dorsal horns of the spinal cord at its center and tapered cranially and caudally along the dorsal columns for a total distance of seven millimeters. By one month after injury the area of necrosis had become a cyst lined by astrocytes ventrolaterally and meningeal cells dorsally. Measurements of lesion length showed a variability of 26%. This model of spinal cord trauma produces a lesion that is sufficiently reproducible to be suitable for performing studies aimed at tissue preservation and repair.

We present the first in vivo study using Optical Coherence Tomography (OCT) as the imaging device for lenticular cataracts in the geriatric rhesus monkey. OCT is a non-invasive imaging technique that produces a 2D cross sectional image of intraocular tissue similar to ultrasound B scan. In OCT the images are formed by measuring optical reflections from the tissue. Eighteen geriatric subjects with documented lenticular opacities and one control subject were imaged. The OCT images produced are compared to current and previous clinical cataract grading exams and slit-lamp photography. Histopathology was collected on one subject and is compared to the OCT image. OCT provides information on nuclear, cortical and subcapsular opacities. The image formation is presented based on a color coded computer generated log reflective scale. The log reflective scale is converted to a qualitative grading system. Although movement and shadow artifact can occur, these are readily identifiable and can be differentiated from underlying lenticular abnormalities. OCT has great potential to assist in further characterization of cataracts.

Thirty patients were surgically treated for discoid menisci at our institution from 1972 to 1987. All developed Fairbank's changes if followed more than 5 years. Between 1980 and 1987 we saw 25 patients with menisci over 50% of the size of the femoral condyle by magnetic resonance imaging or arthrographic examination. Surgical criteria have been anteroposterior hypermobility and arthroscopic evidence of rupture in patients with disabling symptoms. Of the 21 patients undergoing surgery since 1980, 99 (43%) have developed Fairbank's changes, all having been treated by partial meniscectomy or meniscectomy plus posterior repair. Follow-up arthroscopy in five patients revealed distinctly abnormal but relatively stable menisci. Partial meniscectomy for discoid menisci by the Watanabe classification is recommended if symptoms are disabling and the menisci is significantly torn. Repair must be added if the posterior horn is unstable.

In 1990, a randomized, double-blind study was initiated to evaluate the use of an eight-point conservative treatment program in carpal tunnel syndrome. A total of 160 patients were delineated with symptoms of carpal tunnel syndrome. These patients were then divided into two groups. Both groups were subjected to an ergonomically correct eight-point work modification program. A counterfeit low level laser therapy unit was utilized in Group A, while an actual low level laser therapy unit was utilized in Group B. The difference between Groups A and B was statistically significant in terms of return to work, conduction study improvement, and certain range of motion and strength studies.

Recent scientific studies evaluating laser energy for tissue welding and thermokeratoplasty have demonstrated that the application of laser energy at non-ablative levels can alter collagen's structural and biochemical properties. The application of non-ablative laser to the human shoulder joint capsule in patients with glenohumeral instability has been found to enhance stability of the joint. Based on the collective findings of these studies, we hypothesized that thermal modification of dense collagenous tissues such as joint capsule, ligament, and tendon can be achieved by applying non-ablative laser energy. The purpose of this study was to evaluate the effect of laser energy at non-ablative levels on joint capsular mechanical properties in an in vitro rabbit model. Twelve mature New Zealand white rabbits, ranging from 3.73 to 5.33 kg (4.49 +/- 0.44; mean +/- SD), were used for this experiment. Animals were euthanized and two 5 mm X 20 mm specimens were collected from the medial and lateral portion of the femoropatellar joint of each rabbit under a dissecting microscope; therefore four specimens were collected from each rabbit (right medial, right lateral, left medial, left lateral). Specimens were divided into four groups using a randomized block design; a control group and 3 laser power settings (5 watts (5 W), 10 watts (10 W), 15 watts (15 W)). Laser energy was applied using the Ho:YAG laser in four transverse passes across the tissue at a velocity of 2 mm/sec and distance from the tip of the handpiece to the synovial surface of the specimen set at 1.5 mm in a 37 degree(s)C tissue bath of lactated Ringer's solution. Forty-eight specimens (n equals 12) were mechanically tested to determine single cycle structural properties (stiffness) and viscoelastic properties (% relaxation) before and after laser treatment. Shrinkage of the tissue and the loads required to return specimens to their original length were recorded after laser treatment. The application of laser energy resulted in 9%, 26%, and 38% reduction in capsular tissue length for the 5 W, 10 W, and 15 W group, respectively. Tissue shrinkage was significantly and strongly correlated with energy density (p < 0.0001; R² equals 0.80). Laser energy caused a significant decrease in tensile stiffness only in the 10 W and 15 W groups (p < 0.05). There was a significant but weak correlation between energy density and post-laser stiffness values (p < 0.0001; R² equals 0.34). Laser energy did not change the relaxation properties of capsular tissue at any energy density when compared to pre-laser values (p > 0.05; (Delta) equals 29% at power equals 0.8). There was no significant correlation between energy density and relaxation properties of the tissue (p > 0.05). The loads required to return specimens to their original length were significantly lower for the 5 W group (3.6 +/- 5.1 N) than for the 10 W (15.0 +/- 6.2 N) and 15 W (14.0 +/- 5.2 N) groups. There was a significant correlation between energy density and the load required to return the specimen to its original length (p < 0.0001; R² equals 0.58). This study demonstrated that significant capsular shrinkage can be achieved with the application of non-ablative Ho:YAG laser energy without detrimental effects on the viscoelastic properties of the tissue, although at higher energy densities, laser energy did lessen capsular stiffness properties.

Lasers have been used for symptomatic Benign Prostatic Hyperplasia (BPH) in both contact and non-contact modes with reported success rates equivalent to that of Transurethral Resection of Prostate (TURP). A new high power diode laser (Phototome), capable of delivering up to 50 watts of 1000 nm wavelength laser power via a 1 mm quartz fiber, was used to treat 15 patients with symptomatic BPH. Five patients had acute retention, 3 had long term catheter (7 - 48 months), and 8 had severe prostatism. Spinal anesthesia was used in 11 patients, and 4 patients had local anesthesia and intravenous sedation. Four quadrant coagulation with an angle firing probe delivering 50 watts of laser power for 60 seconds in one quadrant was used as the core of the treatment in 11 patients, contact vaporization of BPH tissue was performed in one patient using a 4.5 mm ball tip was used in one patient and three patients with bladder neck stenosis had bladder neck incision performed using a 1 mm quartz fiber delivering 30 watts of laser power. A foley catheter was left indwelling and removed after 5 - 7 days. All patients except one were catheter free after a mean of 8 days. One patient continued to have severe prostatism and had a TURP performed with good results after 3 months of his laser prostatectomy procedure. AUA symptom scores available in 11 patients was found to be 4 after 1 - 3 months of the initial procedure.

We have developed a two-wavelength spectrophotometer for in vivo monitoring of indocyanine green (ICG) concentration. Light from two laser diodes, one with output at 788 nm (near the optical absorption peak of ICG) and the other with output at 905 nm (where the optical absorption of ICG is essentially zero), is coupled into small-diameter multimode optical fibers which transport the light to the tissue under investigation. A third optical fiber collects the reflected and remitted light and transports it to a photodetector. The fibers can either be placed on the surface of the tissue or implanted using a hypodermic needle. By analyzing the intensity of the reflected light from the two light sources, we can accurately predict the concentration of ICG present over a wide range of scattering coefficients of the tissue. We have characterized the performance of the spectrophotometer using tissue phantoms composed of suspensions of Intralipid^TM as a scatterer (0.1 - 3.0%), with ICG concentrations ranging from 100 nM to 20 (mu) M.

Photodynamic therapy (PDT) effectively inhibits fibrocellular intimal hyperplasia (FCIH) two and four weeks after arterial traction balloon injury in rat carotid arteries. The aim of the present study was to assess the long term effects of PDT in this rat model of FCIH. 5- aminolaevulinic acid-induced protoporphyrin IX was used to sensitize rats for PDT after traction balloon arterial injury to the whole of the left common carotid artery. Rats were sacrificed at intervals of six to 26 weeks, and perfusion fixed and H and E stained sections were analyzed using computerized morphometry. PDT inhibition of FCIH was only partial at these late times. The amount of FCIH present increased with increasing time after injury. The late occurrence of FCIH appeared to be due to migration of FCIH from balloon injured areas outside the PDT treated field as a result of the traction injury being applied to the whole carotid. We recommend segmental balloon injury rather than the traction injury of the whole common carotid injury for future studies in this model.

Mechanical injury during pulsed holmium laser ablation of tissue is caused by rapid bubble expansion and collapse or by laser-induced pressure waves. In this study the effect of pulse duration on the photomechanical response of soft tissue during holmium:YAG laser ablation has been investigated. The dynamics of laser-induced bubble formation was documented in water and in transparent polyacrylamide tissue phantoms with a water concentration of 84%. Holmium:YAG laser radiation ((lambda) equals 2.12 micrometers ) was delivered in water or tissue phantoms via an optical fiber (200 or 400 micrometers ). The laser was operated in either the Q- switched mode ((tau) _p equals 500 ns, Q_p equals 14 +/- 1 mJ, 200 micrometers fiber, H_o equals 446 mJ/mm²) or the free-running mode ((tau) _p equals 100 - 1100 microsecond(s) , Q_p equals 200 +/- 5 mJ, 400 micrometers fiber, H_o equals 1592 mJ/mm²). Bubble formation was documented using a fast flash photography setup while simultaneously a PVDP needle hydrophone (40 ns risetime), recorded pressures. The effect of the pulse duration on the photomechanical response of soft biological tissue was evaluated by delivering 5 pulses of 800 mJ to the intimal side of porcine aorta in vitro, followed by histologic evaluation. It was observed that, as the pulse duration was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated, cylindrical shape for the longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. A thermo- elastic expansion wave was measured only during Q-switched pulse delivery. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in water as well as in the gel. The amplitude of the pressure wave depended strongly on the size and geometry of the laser-induced bubble. The important findings of this study were (1) the magnitude of collapse pressure wave decreased as laser pulse duration increased, and (2) mechanical tissue damage is reduced significantly by using longer pulse durations (> 460 microsecond(s) , for the pulse energy used).

Present day XeCI excimer laser coronary angioplasty (ELCA) with multifiber catheters is a safe and efficacious therapeutic modality. However, ELCA related complications, such as perforation, acute closure and arterial wall dissection, have been reported. These complications are at least partly attributed to vascular wall damage inflicted by fast expanding water vapor bubbles and insoluble gas induced by excimer laser pulses. It has been shown that the single pulse fluence threshold for the formation of a fast expanding bubble is about 20 mJ/mm2. Also, it has been observed that the gas yield increases sharply above 30 mJ/mm2. Therefore, it is conceivable that the vascular damage in ELCA caused by fast expanding bubbles and the accumulation of insoluble gas may be reduced by reducing the size and strength of the fast expanding bubbles and the gas yield by using fluences below 20 mJ/mm2.

The concept of interstitial laser coagulation (ILC) of the prostate is the generation of intraprostatic lesions of large volumes, which secondarily are resorbed. In previously published experimental and clinical studies Nd:YAG lasers in combination with specially designed light guides were used. The aim of this study was to examine the suitability of diode lasers to be used in ILC. Diode lasers of various wavelengths (805 nm, 830 nm, 950 nm and 980 nm) with different interstitial applicators (predominantly diffusor tips) were tested in vitro (potatoes, turkey muscle, porcine liver) and in vivo (canine prostate). In vitro experiments were done with various powers and radiation times in order to evaluate the maximum lesion size achievable without tissue carbonization. This depended on the length of the applicator and could measure more than 20 mm. To get large lesion volumes with short radiation times, but to avoid charring, in vivo graded powers were favorable. These were optimized for some systems. In the canine prostate, lesion diameters of up to 15 mm were achieved. For clinical use, interstitial applicators were inserted into the bulky BPH transurethrally through a cystoscope under direct vision, either directly or aided by an introducer system. The number of fiber placements depended on the size and configuration of the gland and varied between 3 and 16. With the 980 nm diode laser and an applicator with conical beam pattern, irradiation was performed for 3 minutes per fiber placement using stepwise reduced power (20 W for 30 s, 15 W for 30 s, 10 W for 30 s and 7 W for 90 s). With the 830 nm diode laser and diffusor tip, the initial power of 10 W was reduced to 5 W within 4 minutes total radiation time. From 1993, 19 patients were treated with diode lasers (830 and 980 nm). Three months follow-up in 15 patients treated with 830 nm showed an AUA-score change from 18.9 to 5.9 and a peak flow rate change from 7.8 to 15.2 ml/s.

Persistent Frenulum and Fibropapillomas are commonly encountered diseases of young bulls. Both are amenable to simple resection with ligation of bleeders followed by mucosa suturing. Sexual rest for several weeks is generally required. Carbon dioxide laser was applied in resection of both these two maladies in six bulls (2 Persistent Frenulum, 4 with fibropapillomas) without the need for ligation of bleeders or mucosal suturing. No immediate postsurgery complications occurred related to the laser being used and potential recurrence of fibropapilloma neoplasia did not occur. The CO₂ laser, compared to the steel scalpel, provided better visibility and improved hemostatic capabilities for performing the resection. The CO₂ laser incisions healed completely by two weeks postirradiation, and the bulls required only one week sexual rest to allow healing to progress prior to entering an active breeding program.

A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

Seventeen patients with subglottic or tracheal stenosis were treated with laser surgery. Six patients had airway compromise caused by malignant tumors. Sixteen patients required emergency endolaryngeal laser surgery, and satisfactory results were achieved in 12 obtaining an adequate lumen for ventilation. Five patients with airway tumors underwent laser surgery to increase the airway lumen, however, only one patient showed excellent results, with a sufficient airway lumen not being obtained in the other. Airway obstructions due to tumors can be treated satisfactorily by laser surgery, although long term postoperative follow up confirmed recurrence of tumor in most cases.

The CO₂ and KTP/532 lasers have been used in the treatment of an allergic and hypertrophic rhinitis for the past several years. As we know, the laser enables a surgeon to perform the operation with minimum hemorrhage and minimized pain, during and after the procedure. Additionally many of these operations can be performed under local anesthesia instead of general anesthesia, on an outpatient basis. The laser is used to irradiate the mucous membranes of the inferior turbinates. Vaporization and cutting is easily done. Post operative management of the local operated area is easy. The advantages of laser surgery over regular surgical techniques are supreme for intranasal operations when performed under local anesthesia.

Investigation of the inner ear is still subject of basic research. Due to the small structures of the inner ear every suggested measurement technique, which includes loading of moving parts, will not be able to detect the oscillations correctly. Therefore an optical approach detecting microvibrations in the cochlea will be discussed. In heterodyne interferometry as compared to classical interferometry two slightly different light frequencies for the reference and object beams are used. The vibration of the object is detected as a modulation of the phase of the detector signal. Many restrictions on the design of our new interferometer caused by the properties of the tissue of the membranes in the cochlea and by the anatomic and geometric shape of the surrounding of the cochlea, needed to be taken into account. A confocal fiber optic heterodyne interferometer with a miniaturized sensor head was built. To improve the optical properties of the sensor head the combination of a gradient index lens and a hologram is under test. The selected wavelength of 830 nm should allow an investigation of layered tissues. It is possible to detect amplitudes down to 0.3 angstroms in a frequency range of 500 Hz to 50 kHz with a simulated object reflectivity of 0.02%.

It has been proposed that atherosclerotic plaques vulnerable to disruption and thrombosis have a lipid-rich core covered by a thin cap. However, a method to detect those plaques has not been established. We hypothesized that such plaques are yellow due to reflection of the yellow lipid core through a thin cap which may be detected by angioscopy. We developed software to quantify yellow color saturation in digitized angioscopic images.