Numerical simulations have been performed to investigate the light distribution in strongly scattering tissues for collimated laser beams. However, very little is known for the propagation of converging laser beams with large cone angles for the lack of efficient algorithms to deal with the difficult boundary conditions. Furthermore, the important effect of surface roughness on the light distribution inside the skin tissues has not been studied. We developed a new Monte Carlo method to simulate the distribution of photon density of converging laser beams propagating in skin tissue phantoms. This method can be used to obtain directly the photon density distribution in the framework of radiative transfer theory. We calculated the steady-state distributions of the photon density and found several important features that are uniquely related to the propagation of the converging beams in skin tissues. We also conducted preliminary study on the effect of roughness of skin surface on the light distribution inside the skin tissue with the new Monte Carlo method.

Cryogen spray cooling (CSC) can protect the epidermis from non-specific thermal injury during laser treatment of port wine stains and other hypervascular cutaneous malformations. Knowledge of skin internal temperatures in response to CSC is essential for optimization of this technique. We used an epoxy resin compound to construct a kind phantom and measured its internal temperatures in response to cooling with different cryogens at various spurt durations, spraying distances, and ambient humidity levels. The measured temperature distributions during CSC were fitted by a mathematical model based on thermal diffusion theory. For spurt durations up to 100 ms, temperature reduction within the phantom remained confined to the upper 200 μm, and was affected by spraying distance. Depending on the cryogen used, temperature reductions up to 45°C could be measured 20 μm below the surface at the end of a 100 ms spurt. However, the cryogen film temperature on the epoxy resin surface was up to 35°C lower, indicating lack of perfect thermal contact at the cryogen film-phantom interface. Theoretical predictions were within 10% of measured temperatures. Ice formation occurred following termination of the spurt and was influenced by the ambient humidity level.

Quantitative data regarding photothermal and damage processes during pulsed laser irradiation of blood are necessary to achieve a better understanding of laser treatment of cutaneous vascular lesions and improve numerical models. In this study, multiple experimental techniques were employed to quantify the effects os single- pulse KTP laser (λ = 532 nm, τ_p= 10 ms) irradiation of whole blood in vitro: high-speed temperature measurement with a thermal camera in line-scan mode (8 kHz); optical coherence tomography; and transmission measurement with a co-aligned laser beam (λ=635 nm). Threshold radiant exposures for coagulation (4.4-5.0 J/cm²) and ablation (~ 12 J/cm²) were identified. Thermal camera measurements indicated threshold coagulation temperatures of 90-100°C, and peak temperatures of up to 145°C for sub-ablation radiant exposures. Significant changes in coagulum thickness and consistency, and a corresponding decrease in transmission, were observed with increasing radiant exposure. The Arrhenius equation was shown to produce accurate predictions of coagulation onset. The significant of dynamic effects such as evaporative loss and dynamic changes in optical properties was indicated. Implications for numerical modeling are discussed. Most importantly, the threshold temperatures typically quoted in the literature for pulsed laser coagulation (60-70 °C) and ablation (100 °C) of blood do not match the result of this study.

While feedback control is widespread throughout many engineering fields, surgical instruments with embedded feedback control systems are uncommon. To improve the effectiveness of microsurgical techniques, we are presently developing a semi-autonomous robotic surgical tool as an alternative approach to treatment of skin hemangiomas like nevus flammus. Current PWS phototherapy relies on selective absorption of optical radiation by the ectatic blood vessels in a PWS resulting in thermally-mediated vessel necrosis. Although shown to be effective,heating of the surrounding tissue by photon absorption results in unacceptable collateral damage. The 'Smart Scalpel' approach employs optical reflectance spectroscopy to selectively target blood vessels in a PWS for heating with a focused laser beam. Collateral damage to adjacent tissue is substantially minimized and continuous imaging throughout the procedure allows modification of the delivered therapy to optimize therapeutic outcomes. Our work reported here involves optical system design and construction, initial quantification of imaging system resolution and contrast, and preliminary verification of the imaging and targeting strategies.

Presented here are experimental results for a new high- energy/intensity polymer dye laser, with different laser resistant modified polymer elements impregnated with pyrromethene dyes. These polymers manufactured in Russia. They were pumped by a frequency doubled Medlite IV Nd:YAG laser developed by Continuum Biomedical with pulse energies up to 560mJ, pulse width 5 to 7ns with a beam sizes of 6mm and intensities up to 400MW/cm². A maximum dye laser output energy up to 450mJ at 585nm and up to 310mJ at 650mm were achieved in broadband operation mode. Overall efficiency > 80% at 585nm and > 50% at 650 nm were obtained at pump fluences up to 2J/cm². Variable wavelengths of 560 and 585nm in the yellow spectral range and 630 and 650nm in the red spectral range were demonstrated by choosing the proper polymer element with different laser dyes and a specially designed dichroic high reflector. A stable output of 250mJ for more than 50,000 pulses at 585nm and 150mJ for more than 20,000 pulses at 650nm has been achieved with the Multiple Dye Laser Handpiece developed by Continuum Biomedical. This was achieved with pump energies up to 400 mJ.

This review tackles the problem of further developing laser- ultrasonic medical technologies and gives the comparison of different laser and ultrasound combinations. The features of combined influence on biotissue are explicated with due regard for mechanic, ultrasonic (US), and thermal effects. The review present the effect of self-cleaning an optical fiber tip from the laser destruction products of biotissue, the result of research on the possibility of laser-US technology applications in endoscopy, and the ways of suppressing unwanted bending oscillations. Various spheres and peculiarities of applying laser-US technologies are discussed, including microsurgery, cosmetology, transcutaneous drug delivery, and the treatment of chronic prostatitis and infected wounds. Furthermore, the analysis of transcutaneous drug delivery methods employing a portable pulsed Er:YAG laser is presented. Drug diffusion has been shown to be enhanced under acoustic and US effects. The photo-vacuum drug injection mechanism recently suggested is discussed. It turned out that laser-US technology can be suitable for both impregnating the photosensitizer in local photodynamic therapy procedures and conducting microsurgery operations involving drug injection. Treatment of infectious processes based on the bactericidal action of photosensitizers and ultrasound due to the cavitation effect in solutions is described. An additional therapeutic effect can be achieved via the US intermingling of solutions with their simulations illumination by a matrix of red lasers or light diodes. An outlook on further developing laser-US technology and the ways of its apparatus realization are considered.

Recent laser-tissue soldering work in our lab has demonstrated the feasibility of building a solder bond from individually coagulated small droplets using a precision pipette for the deposition of the solder droplets. This method of using small, precise volumes of solder to build a bond may result in stronger and more reproducible bonds than coagulating an equivalent large volume of solder all at once. We have investigated the technique further in this study. The solder was dispensed onto the intimal side of a bovine aorta substrate and irradiated with an 808nm diode laser. A bond was created across an incision in the tissue substrate by alternately dispensing and coagulating each small volume of solder, or by coagulating a single large equivalent volume. Acute strength analysis was performed on the solder bond. Future work will concentrate on testing a bench-top solder dispensing device and investigating the feasibility of turning the deice into a prototype tool for clinical applications.

An in vitro study was performed using an 808nm-diode laser in conjunction with indocyanine green-doped albumin protein solders to repair bovine aorta specimens. Investigations were conducted to determine optimal solder and laser parameters for tissue repair in terms of tensile strength, temperature rise and damage and the microscopic nature of the bonds formed. Liquid and solid protein solders prepared from 25% and 60% bovine serum albumin (BSA), respectively, were compared. The tensile strengths of the repairs were greatly improved with an increase in BSA concentration from 25% to 60% and a reduction in ICG dye concentration from 2.5 mg/ml to 0.25 mg/ml. Increasing the later irradiance and thus surface temperature resulted in an increased severity of histological injury. Thermal denaturation of the tissue substrate increased laterally and in depth with higher temperatures. Optimal repairs in terms of bond strength and thermal damage were achieved by denaturing a solid protein solder composed of 60% BSA and .025mg/ml ICG with an irradiance of 6.4 W/cm². Using this combination of solder and laser parameters, surface temperatures were observed to reach 85±5°C with an average temperature difference across the solder strips of 15°C across a thickness of 150 μm. Histological examination of the repairs formed using these parameters showed negligible evidence of collateral thermal damage to the underlying tissue. Scanning electron microscopy suggested albumin intertwining within the itssue collagen matrix and subsequent fusion with the collagen as the mechanism for laser tissue soldering.

We evaluated the effect of changes in laser spot size and beam profile on the thermal denaturation zone produced during laser skin welding. Our objective was to limit heating of the tissue surface, while creating enough thermal denaturation in the deeper layers of the dermis to produce full-thickness welds. Two-cm-long, full-thickness incisions were made on the backs of guinea pigs, in vivo. India ink was used as an absorber. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. Cooling times of 10.0 s between scans were used. Laser spot diameters of 1, 2, 4, and 6 mm were studied, with powers of 1, 4, 16, and 36 W, respectively. The irradiance remained constant at 127 W/cm². 1, 2, and 4 mm diameter spots produced thermal denaturation to a depth of 570 ± 100 μm, 970 ± 210 μm, and 1470 ± 190 μm, respectively. The 6-mm- diameter spot produced full-thickness welds (1900 μm), but also burns due to the high incident power. Monte Carlo simulations were also conducted, varying the laser spot diameter and beam profile. The simulations verified that an increase in laser spot diameter result in an increase in the penetration depth of radiation into the tissue.

A thermal camera was used to measure surface temperatures during laser skin welding to provide feedback for optimization of the laser parameters. Two-cm-long, full- thickness incisions were made in guinea pig skin. India ink was used as an absorber. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing a pulse duration of approximately 100 ms. Cooling durations between scans of 1.6, 4.0, and 8.0 s were studied with total operation times of 3, 5, and 10 min, respectively. A laser spot diameter of 5 mm was used with the power constant at 10 W. Thermal images were obtained at 30 frames per second with a thermal camera detecting 3.5 micrometers radiation. Surface temperatures were recorded at 0, 1, and 6 mm from the center line of the incision. Cooling durations between scans of 1.6 s and 4.0 s in vitro resulted in temperatures at the weld site remaining above ~65°C for prolonged periods of time. Cooling durations between scans as long as 8.0 s were sufficient both in vitro and in vivo to prevent a significant rise in baseline temperatures at the weld site over time.

Cryogen spray cooling of the tissue surface was investigated for laser welding applications. Benefits include reduced thermal damage to the papillary dermis and reduced operation time. Two-cm-long, full-thickness incisions were made on the backs of guinea pigs, in vivo. India ink was used as an absorber and clamps were used to appose the incision edges. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing ~100 ms pulses. A 4-mm-diameter laser spot was used with a constant power of 16 W. The total operation time was 60 or 120 s. Cryogen was delivered in spurt durations of 20, 60, or 100 ms, with 2 or 4 s between spurts. The working distance was approximately 12 cm, and the spray covered an area of about 5.0 x 5.0 cm. Control welds were irradiated for 20, 40, or 60 s. Total operation times were reduced from 10 min without dynamic cooling to 1 min with dynamic cooling. Optimal tensile strength was 1.7 ± 0.7 kg/cm², comparible to stengths of 2.1 ± 0.7 kg/cm² reported in previous studies without cryogen cooling (p>0.25). Thermal damage in the papillary dermis measured 320 ± 80 μm.

We have been investigating the potential applicability of photodynamic therapy for the treatment of benign and malignant disease of the prostate. Both transurethral and transperineal approaches to the delivery of light to the tin ethyl etiopurpurin sensitized canine prostate have been studied. Pharmacologic studies were performed and suggested that delaying light treatment for 7 days after drug administration would maximize the desired effect on the targeted prostatic tissue while minimizing the damage to surrounding bladder and rectum. A total of 12 dogs were treated with transurethral light alone (n=6) or the combination of transurethral light and transperineal light one week after tin ethyl etiopurpurin administration. (Previous studies have shown that light alone has no effect on prostate size or histology.) Animals were euthanized 48 hours and 3 weeks after completion of treatment (drug, 1mg/kg day 0, light [400mw/750sec]day 7). Tissue response was determined by gross and microscopic examination. Additionally, pre- and post- treatment transrectal ultrasounds were compared to assess changes in prostate volume and tissue echogenicity. The combination of transurethral and transperineal light results in extensive destruction of glandular epithelium with minimal damage to surrounding structures. Prostate volumes decreased by an average of 52%. Untreated areas were found to lie greater than 0.5 cm from the light diffuser. These studies have encouraged us to continue to investigate this modality as a technique for total ablation of prostatic glandular epithelium.

Photodynamic therapy (PDT) principles were evaluated in management of benign prostatic hyperplasia (BPH) in a canine model. Five dogs were injected with benzoporphyrin derivative (BPD) and samples of prostate, bladder, urethra and rectum were taken at 1, 2, 3 and 4 hours and analyzed for BPD. Next, 16 dogs were treated with 100 Joules at 690 nm light form argon dye laser 1 hour after administration of BPD at 0.5 mg/kg using cylindrical diffuser tip fiber passed transurethrally. The prostates were harvested weekly up to 4 weeks and the size of the lesion was measured and the prostates were examined. Prostate had the highest BPD levels. Hemorrhagic lesion of 2.5 cm in diameter was noted at 1 week after PDT. At 3 and 4 weeks there were changes of glandular atrophy in the periurethral region. Minimally invasive technique of transurethral PDT causes glandular and stromal changes in the periurethral zone and has potential in the treatment of BPH.

Management of neurogenic bladders with high pressures and poor compliance often requires surgical enlargement of the bladder utilizing small or large bowel or stomach. The bowel segments usually retain their absorptive and secretory properties causing several complications which include hyperchloremic metabolic acidosis for small and large bowel segments, hypochloremic metabolic alkalosis for stomach segments, increased risk of bacteriuria, stone formation, altered hepatic metabolism and altered drug metabolism. There is also the potential risk of developing cancer at the anastomotic site.

The clinical outcome of the holmium laser resection of the prostate (HoLRP) shows similar results when compared to the transurethral resection of the prostate (TURP). Our efforts had ben to solve certain problems in the clinical application, e.g. the angle fiber/tissue in the apex area of the prostate and the movements of the shaft during the resection. The authors present a new application system for the laser resection and review their own experience in the development and clinical application system for the laser resection and review their own experience in the development and clinical application of Holmium:YAG laser technology for prostatectomy. Between 3/97 and 12/98, 79 patients were treated with the holmium laser resection of the prostate. The laser resections with the specially designed laser-resectoscope were performed from 5/98-12/98 (n-28 patients). With the new resectoscope a proper instrumentation became available. A ceramic tip mounted lever provided a deflection at an angle of 20° of the fiber without any damage of the applicator during the laser application. The manipulation of the fiber within the shaft in all three directions makes an enucleation of the prostate possible. The mean operating time was 63 minutes. There were no acute perioperative complications. The mean postoperative AUA symptom score was 9.1 compared to 22.5 preoperatively. The mean postoperative peak flow rate was 19.1 ml/s compared to 7 ml/s preoperatively. The new technical device improves holmium laser prostate resection and a combination of techniques provides an effective method with minimal complications and morbidity.

Introduction: Due to the unavailability of suitable endoscopic instruments, pediatric patients have not benefited fully from the technological advances in the endoscopic management of the upper urinary tract. This limitation may be overcome with the Holmuim:Yttrium-Aluminum-Garnet(Ho:YAG) laser delivered via small instruments. To date, there is no published report on the use of this modality in children. Purpose: We evaluated the indications, efficacy, and complications of endourological Ho:YAG laser surgery in the treatment of pediatric urolithiasis, posterior urethral valves, ureterocele and ureteropelvic junction obstruction. Methods: The patient population included 10 children with renal, ureteral and bladder calculi, 2 children with posterior urethral valves, 2 children with obstructing ureteroceles, 2 children with ureteropelvic junction obstruction and 1 child with a urethral stricture. Access to the lesions was either antegrade via a percutaneous nephrostomy tract or retrograde via the urethra. A solid state Ho:YAG laser with maximum output of 30 watts (New Star lasers, Auburn, CA) was utilized as the energy source. Results: A total of 10 patients underwent laser lithotripsy. The means age of the patients was 9 yrs (5-13 yrs). The average surface area of the calculi as 425.2 mm² (92-1645 mm²). 8 of the patients required one procedure to render them stone free, one patient had a staghorn calculus filling every calyx of a solitary kidney requiring multiple treatments and one other patient with a staghorn calculus required 2 treatments. There were no complications related to the laser lithotripsy. Two newborn underwent successful ablation of po sterious urethral valves. Two infants underwent incision of obstructing ureteroceles with decompression of the ureterocele on postoperative ultrasound. Two children underwent endypyelotomy for ureteropelvic junction obstruction. One was successful an done required an open procedure to correct the obstruction. One child underwent successful direct visual urethrotomy for a urethral sticture. Conclusions: The Ho:YAGs ability to pulverize urinary calculi make it an obvious choice for lithotripsy in children. The advantages of this technology are the ability to precisely apply the laser using small fibers, and the laser's ability to pulverize calculi with minimal trauma to surrounding tissue. The Ho-YAG laser is also superior to other modalities in the treatment of secondary ureteropelvic junction obstruction. We do not feel the Ho:YAG laser is superior to the curren treatment methods for the treatment of posterior urethral valves and obstructed ureteroceles.

Woundhealing is a complex phenomenon which varies according the type of tissue but is also depending from the type of tissue injury. Electrocautery mainly induces coagulation necrosis while thermal damages induced by the Holmium laser primarily lead to tissue vaporization which may induce less tissue injury. The aim of this study was to evaluate the healing process of the Holmium laser induced lesions compared to electrocautery induced lesions in urothelial tissue by assessing the inflammatory response and myofibroblast behavior in sequential healing phases. A surgical wound was created in the urinary rat bladder of 32 rats either by electrocautery or by laser (N=16). The inflammatory response, the total lesion depth and the myofibroblast activity during woundhealing was then analyzed on a qualitative basis on days 0/2/4/8. The overall inflammatory response was comparable in both groups up to days two and four. However, at day eight less cellular inflammatory reaction and less myofibroblast activity was found in the specimen of lesions created by the Holmium laser. These results suggest that wound repair may be a less invasive process after Holmium laser than electrocautery.

Background: Because of difficulties with suture placement during minimally invasive procedures, many have sought alternative methods of creating tissue anastomoses. Although well studied, thermal laser tissue bonding has the potential of causing collateral thermal injury. Non-thermal tissue bonding agents, which cross-link proteins when activated with light, are currently being explored. We recently reported successful non-thermal bonding using tetrabromorhodamine (TBR). The bond was stronger than sutured repairs but weaker than laser thermal bonding. We currently report our ex-vivo experience with an alternate agent, riboflavin-5-phosphate and compare these results to thermal bonding and TBR. Methods: Rabbit ureteral segments were harvested, divided and placed over internal stents. End-to-end anastomoses were created using several methods: 1)Photochemical bonding: The activating light source used was an Argon laser at a radiant exposure of 90 J/cm². The photoalkylating agents used were TBR combined with collagen (n=15) or riboflavin combined with fibrinogen (n=12). 2)Thermal laser bonding: (n=12) 50% albumin and indocyanine green solder irradiated with the Diomed diode laser (Diomed Corp) at a radiation exposure of 119.4-597 J/cm². 3)Sutured anastomoses: This was performed with 7-0 Dexon interrupted sutures. Control experiments using fibrinogen alone, TBR alone, riboflavin alone and collagen alone were also performed. Bond strength was evaluated by measuring the anastomotic leak pressure against a column of water. Results: Thermal and photochemical bonding with both TBR and riboflavin were significantly stronger than sutured repairs. The bonds created wtih TBR (74±49 cmH₂O) were weaker than those created by thermal welding (132±50cmH₂O) and riboflavin (115±64cmH₂O). ALP measurements in the control experiments were below 10 cmH₂O. Conclusion: Photochemical bonding with riboflavin can achieve similar bond strength to thermal welding without the risk of damage to surrounding tissues. We are currently evaluating in vivo efficacy of this modality. This alternative method of tissue bonding for minimally invasive procedures should be further explored.

Background and objective. The human prostate is a glandular organ that has intervening fibromuscular elements. The objective of this study was to evaluate the thermocoagulative effect on the different components of the organ exposed to Nd:YAG laser irradiation using a new ITT optic fiber design. Study design/patients and methods. Twelve fresh transvesical prostatectomy specimens were irradiated ex-situ at 4 to 6 sites using an ITT fiber with laser energies ranging from 900 to 4500 joules applied at times ranging from 60 to 300 seconds corresponding to 10 to 15 watts. The specimens were serially sectioned to include the proximal, mid and distal regions of the centrally coagulated channel. An occular grid was utilized to measure the radius of thermal injury from the margin of the centrally coagulated channel to the furthermost detectable area of thermally induced changes. Results. The maximal extent of thermal injury was seen at the mid-length of the irradiated channel at energy of 2700j (15w/180sec). The fibromuscular compartment of the prostate was more affected (r=855 μm) and showed more interstitial vacuolization and charring than the adenomatous one. Utilization of higher energy doses did not significantly alter the depth of injury but did reduce the extent of interstitial vacuolization of both components. Conclusion. The study indicates that the extent of laser induced coagulative necrosis depends on the histologic architecture of the prostate and also varies in extent along the length of the channel surrounding the fiber.

The mechanism of holmium:YAG lithotripsy is photothermal. Holmium:YAG lithotripsy of uric acid calculi produces cyanide, which is a known, thermal decomposition produce of uric acid. we review our experience with holmium:YAG lithotripsy of uric acid to determine if there is any clinical evidence of cyanide toxicity. A retrospective analysis of all of our cases of holmium:YAG lithotripsy of uric acid calculi was done. Anesthetic and postoperative data were reviewed. A total of 18 patients with uric acid calculi were tread with holmium:YAG lithotripsy by urethroscopy (5), retrograde nephroscopy (2), percutaneous nephrolithotomy (5) or cystolithotripsy (6). Total holmium:YAG irradiation ranged from 1.2 to 331 kJ. No patient had evidence of increased end-tidal carbon dioxide, change sin electrocardiogram or significant decrease in postoperative serum bicarbonate. An 84 year old woman had decreased diastolic pressure of 30 mm Hg while under general anesthesia. No cyanide related neurologic, cardiac or respiratory complications were noted. These data suggest no significant cyanide toxicity from holmium:YAG lithotripsy or uric acid calculi in typical clinical settings. More specific studies in animals are warranted to characterize the risk.

The ideal laser produces discrete wounds in a reproducible manner. The CO₂ laser with its 10.6 micron wavelength is highly absorbed by water, its energy concentrated at the point of impact and the longer wavelength creates less scatter in tissue. The development of binocular endoscopic delivery system for use with binocular microlaryngoscopes have aided in using CO₂ laser to treat patients with subglottic and tracheal stenosis. Often, patients with these disease processes require multiple endoscopic or open reconstructive procedures and my ultimately become tracheotomy dependent. The canine model of subglottic stenosis that has been develop allows testing of new agents as adjuncts to laser treatment. Mitomycin-C is an antibiotic with antitumor activity used in chemotherapy and also in ophthalmologic surgery due to its known inhibition of fibroblast proliferation. Current studies indicate this drug to have significant potential for improving our current management of this disease process.

The results of recent study of cartilage reshaping in vivo are reported. The ear cartilage of piglets of 8-12 weeks old have been reshaped in vivo using the radiation of a holmium laser. The stability of the shape and possible side effects have been examined during four months. Histological investigation shown that the healing of irradiated are could accompany by the regeneration of ear cartilage. Finally, elastic type cartilage has been transformed into fibrous cartilage or cartilage of hyaline type.

Although the successful use of the Ho:YAG laser in nasal turbinate surgery had been reported no clinical study had been performed to assess the clinical outcome in longterm. By means of a pulsed Ho:YAG laser emitting at λ=2080nm (1J/pulse, 3-8 Hz) 57 patients suffering from nasal obstruction due to allergic rhinitis and vasomotoric rhinitis were treated under local anesthesia. The study was conducted by standardized questionnaire, photo documentation, allergy test, mucocilliar test, rhinomanometry, radiology and histology. Within 2 weeks after laser treatment a significant improvement of nasal airflow correlating to the extent of the ablated turbinate tissue could be determined. This effect lasted up until 1 year post treatment resulting in an improved quality of life in more than 80 percent of the patients. Side effects like nasal dryness and pain were rare (<4%), no immediate complications were observed. The total treatment time takes 3-8 min and nasal packing was not necessary after the laser procedure. In conclusion Ho:YAG laser treatment can be performed as an outpatient procedure under local anesthesia with excellent ablation of soft tissue in a short treatment time with promising results.

The histological effects of flash-scanned CO₂ (λ=10.6μm) and pulsed Holmium:YAG (Ho:YAG, λ=2.12μm) lasers were evaluated in human scalp following the creation of hair transplant recipient channels. Ho:YAG laser irradiation created larger zones of thermal injury adjacent to the laser channels than irradiation with the CO₂ laser device. When the two lasers created recipient sites of nearly equal depth, the Holmium:YAG laser caused a larger region of lateral thermal damage (589.30μm) than the CO₂ laser (118.07μm). In addition, Holmium:YAG irradiated specimens exhibited fractures or discontinuities beyond the region of clear thermal injury. This shearing effect is consistent with the photoacoustic mechanism of ablation associated with pulsed mid-IR laser irradiation. In contrast, channels created with the CO₂ exhibited minimal epithelial disruption and significantly less lateral thermal damage. While the Holmium:YAG laser is a useful tool for ablation soft tissue with minimal char in select applications (sinus surgery, arthroscopic surgery), this study suggests that the use of the CO₂ laser for the creation of transplantation recipient channels result in significantly less lateral thermal injury for the laser parameters employed.

Laser radiation can be used to reshape cartilage grafts via thermally mediated stress relaxation. While several studies have addressed the biophysical changes accompanying reshaping, cartilage viability following laser irradiation has not been extensively investigated. The objective of this study was to determine the extent of angioinvasion of irradiated cartilage explant placed onto the chick chorioallantoic membrane (CAM) model. Angioinvasion of the tissue matrix does not occur in viable cartilage tissue, whereas denatured tissue is readily vasculairzed and/or resorbed in vivo. Porcine septal cartilage specimens were removed from freshly sacrificed animals and divided into three protocols (n=10 each group) consisting of an untreated control, cartilage boiled in saline solution for one hour, and a laser irradiated group (Nd:YAG, λ=1.32 μm, 30.8 W/cm², irradiation time = 10 sec). Following laser irradiation, tissue specimens were washed in antibiotic solution sand cut into small cubes (~1.5 mm³). The cartilage specimens were placed onto the surface of twenty CAMs, six of which, survived the entire 14 days incubation period. After incubation, the membranes and specimens were fixed in situ with formaldehyde, an then photographed using a dissection microscope. Cartilage specimens were prepared for histologic evaluation and stained with hematoxylin and eosin. Examination with a dissecting microscope showed no obvious vascular invasion of the cartilage or loss of gross tissue integrity in both the control and laser treated groups. In contrast, boiled specimens appeared to be partially or completely resorbed by the surrounding CAM vascular network. These gross findings were also confirmed by histological examination. In summary, our preliminary studies suggest that cartilage specimens treated using the present laser parameters remain resistant to angioinvasion or metabolism by the CAM, whereas boiled tissue undergoes resorption. Clinically, uncontrolled heating may result in total resorption of cartilage with catastrophic sequelae such as infection, necrosis, and total graft resorption. This study underscores the importance of preserving cartilage viability during laser surgical procedures relying on a photothermal mechanism.

We present first result of using the optical coherence tomography (OCT) in complex clinical studies in laryngology. Mucosa of the upper and middle portions of larynx is of special interest for OCT applications: it is clinically important, easily accessed by an endoscopic OCT probe, and possesses a well defined and rich tomographic structure. We have examined several tens of patients with abnormalities in vocal folds. The diagnosis was made based on clinical data including laryngoscopy and finally confirmed morphologically. When examining larynx mucosa, an endoscopic OCT probe has been introduced through a standard laryngoscope lumen, so that OCT imaging has been performed in parallel with visual observation. The OCT studies have demonstrated that in comparison with stratified healthy mucosa, carcinomatous regions have no tomographically differentiated structure, thus allowing one to exactly define the border of a tumor. Vocal nodules are imaged as poorly scattering regions without clear boundaries under preserved epithelium. Cysts of gland mucosa are seen with OCT as sharply delineated shadows at the depth of several hundred micrometers. We have also examined several patients with carcinoma after a course of radiation therapy and observed different changes in OCT images of adjoining epithelium corresponding to metaplasia, hyperplasia, and sclerosis.

Optical coherence tomography (OCT) was used to image the internal structure of a rat cochlea. Immediately following sacrifice, the temporal bone of a SPrague-Dawley rat was harvested. Axial OCT cross sectional images (over regions of interest, 1 x 1 mm to 2 x 8 mm) were obtained with a spatial resolution of 10-15 μm. The osseous borders of the lateral membranous labyrinth overlying the cochlea and the scala vestibuli, media, and tympani which were well demarcated by the modiolus, Reissner's and the basilar membranes were clearly identified. OCT can be used to image internal structures in the cochlea without violating the osseous labyrinth, and may potentially be used to diagnose inner ear pathology in vivo in both animal and human subjects.

Laryngomalacia is a common cause of airway obstruction in neonates and infants that, when severe, may be treated surgically via laser supraglottoplasty. Despite individual surgeons' successful experience with this technique, an objective broadly applied assessment of patient outcomes has been lacking. This is worrisome since the provision of health care is increasingly judged by the ultimate result: whether a person's quality of life is better for having undergone a particular procedure. Institutions that lack evidence of such benefit will face difficulty in justifying, and in obtaining compensation for, their services. We share our tool for the measurement of outcomes following laser supraglottoplasty. Over the past year, we have found this tool to be easily and rapidly applied. The wide range of possible combinations of patient presentation and the specific anatomic conformation of the laryngomalacia are effectively organized into standard database format, allowing for relevant clinical and anatomic information to be compared to post-operative indicators of outcome. We hope that this discussion prompts the development of similar tools for patient assessment following other laser airway procedures. Our ability as health care provides to control patient care depends upon the presentation of cogent, convincing evidence of improved patient well-being following treatment.

In Otorhinolaryngology the endoscopic appraisal of luminal dimensions of the nose, the throat, the larynx and the trachea is a daily problem. Those concerned with endoscopy know, that endoscopes distort dimensions of examined anatomical structures. To draw conclusions on luminal dimensions from the endoscopic pictures additional measuring devices are required. We developed a new method of measuring luminal dimensions in rigid or flexible endoscopy. For this a laser beam directed radially marks the anatomical lumen of interest in the videoendoscopic vision. The laser ring becomes deformed according to the form of the cavity explored. By keeping the distance defined between the laser ring and the top of the endoscope, the endoscopic video image can be measured. A piece of software developed by us calculates from the pictures the cross sectional area as well as the extension of benign or malign stenosis of the cavity explored. The result of the endoscopic measuring procedure can be visualized 3D on a PC-monitor. We are going to demonstrate the result of our clinical experience in different otorhinolaryngological diseases with the new endoscopic measuring kit in comparison to standard endoscopy. A further perspective is the endoscopic measuring kit in comparison to standard endoscopy. A further perspective is the endoscopic assisted manufacturing (EAM) of anatomical adapted stents, tubes and cannules.

The purpose of this study was to test a new prototype pulsed CO₂ laser to be used for transmyocardial laser revascularization (TMR). We want to determine whether it can reduce thermal damage and mitigate induced ischemia with improvement in contractile reserve of the heart as evidenced by contrast echocardiography at rest and under dobutamine stress. TMR is an emerging surgical strategy for treatment of myocardial ischemia not amenable to conventional percutaneous or surgical revascularization. Eleven pigs underwent amaroid occulder placement on the origin of the circumflex coronary artery. Six weeks laser occlusion of the circumflex coronary artery was documented. TMR was then done on ten pigs using a prototype pulsed CO₂ laser that delivered 8-12 joules energy in 1.5ms with a spot sizes of 1mm. Six weeks after TMR the pigs were restudied and sacrificed. The animals developed significant ischemia after six weeks of ameroid occlusion, at rest (p=0.01) and at peak stress (p=0.004). Wall motion for the ischemic segments improved significantly six weeks after TMR at peak stress (p=0.02). TMR results in an improvement in wall motion in our model of chromic ischemia and improves WMSI significantly during induced stress than at rest.

Current multiple-optical-fiber catheters for excimer laser coronary angioplasty (ELCA) emit pulsed light at 308nm from a xenon chloride (XeCl) excimer laser to remove plaque in occluded arteries. Because the fiber ends, arranged in a closest- packed array, do not cover the entire surface of the catheter tip, these devices ablate holes typically holes typically 75-80 percent of the catheter tip diameter. To increase the ablation effectiveness, an optimally spaced fiber catheter has been designed in which the fiber-to-fiber spacing is increased precisely enough so as to cover the entire catheter tip area with fibers. In vitro and in vivo testing compared the optimally spaced catheter to catheter models currently in clinical use. Although device handling characteristics were found to be identical, the optimally spaced devices removed a significantly greater amount of tissue. This may offer a technical advantage in a clinical setting.

Successful removal of cholesterol ester which is specifically accumulated in the arteriosclerotic region on the arterial walls was achieved by the exposure of 5.75 μm-IR free-electron-lasers (FEL) which is absorbed by C=O stretching vibrations of ester. In this study, chemical bond-changes and decrease in amount of cholesteryl oleate in IRFEL photodynamic processes were examined by Fourier transform IR microspectroscopy (FTIR). We found that the exposure of 5.75μm-FELs induces not only dissociation of ester (RCOOR') bonds but also the oxidation process of the ester (RCOOR') bonds to aldehyde (RCHO) carboxylic acid (RCHOOH), carboxylate (RCOO^-) or ketone (R₂C=O) bonds. Further, we exposed cholesteryl oleate to FELs having wavelength of 5.75μm, 9.40μm and 8.44μm. From changes in absorbance and thickness of the samples, we calculated quantum efficiency Φ for decrease of ester bonds and C-C chains for each wavelength-FEL exposure. Φ was obtained to be 2.1 X 10^-4 for ester bond and 1.2 X 10^-4 for C-C chain by 5.75μm-FELs, 0.9x10^-4 and 2.0x10^-4 by 9.40μm- FELs, and 1.2x10^-4 and 1.0x10^-4 by 8.44μm-FELs. Thus, we can conclude that removal of cholesteryl oleate by IR-FELs has the wavelength sensitivity coming from correspondence between the bonds which absorbs FEL photons and which aimed to remove.

High resolution imaging of intraarterial structure is necessary for the identification of high risk coronary plaque. Optical coherence tomography (OCT), a recently developed technology, is a compact, fiber optic based imaging modality with resolutions between 2-20 μm and real time image acquisition rate. Previous in vitro studies have demonstrated the capability of OCT to identify plaque morphology and distinguish plaques with high lipid content. This work demonstrates the feasibility for OCT imaging of in-vivo intraarterial structures. We demonstrate the detection of microstructural detail and the effects of blood on imaging. Saline injections were required during imaging to reduce the signal attenuation of blood. An axial resolution of 10 μm was achieved. Microstructure within the arterial wall was sharply defined and correlated with histology. OCT shows potential to assist in the risk stratification of plaques and the guidance of interventional procedures, such as stent deployment.

We have shown that bubble expansion and collapse near the interface between two materials with modest property differences produces jet-like interpenetration of the two materials. The bubble dynamics at a water-viscous fluid interface is compared with that at the interface of water with a weak elastic-plastic material. We find that, despite rather similar behavior during bubble growth and the initial portion of bubble collapse, the terminal jetting behavior is quite different, even in direction. The elastic-plastic properties chosen are representative of real and surrogate thrombus. Simulations using the elastic-plastic model agree quantitatively with laboratory thrombolysis mass-removal experiments. In our earlier simulations of laboratory experiments, walls have been remote so a to not affect the dynamics. Here we present 2D simulations of thrombolysis with water over elastic-plastic surrogate thrombus in a geometry representative of the clinical situation. The calculations include thin cylindrical elastic walls with properties and dimensions appropriate for arteries. The presence of these artery walls does not substantially change the interface jetting predicted in unconfined simulations.

Hospital records reviewed from 1986-1998 determined that 18 horses were presented for correction of epiglottic entrapment by the aryepiglottic fold. All horses had a history of an abnormal respiratory noise and/or exercise intolerance. In conjunction with epiglottic entrapment, 10 horses had dorsal displacement of the soft palate. Initial confirmation of the epiglottic entrapment was made by endoscopic examination. In addition, 3 horses had radiographs taken of the larynx and pharyngeal region to determine the length of the epiglottis.Laser surgical treatment was performed on the horses in a standing position under sedation. The treatment consisted of axially dividing the aryepiglottic fold from the base of the epiglottis to the tip or beyond by means of a laser fiber introduced through the biopsy channel of an endoscope. The Nd:YAG laser was applied transendoscopically to 11 horses using free fiber technique. Three horses received transendoscopic laser correction using the 808-nm diode laser with the fiber in contact configuration. A combination of both 808-nm diode laser and Nd:YAG lasers were used to facilitate correction in the last 4 horses. Partial re-entrapment occurred in 2 out of the 3 cases in which the 808-nm diode laser was used as a single modality for correction. This did not occur in the horses that received either the Nd:YAG laser treatment or Nd:YAG laser treatment in combination with the 808-nm diode laser. Horses that received either 808-nm diode laser irradiation alone or 808-nm diode laser irradiation in combination with Nd:YAG laser appeared to have less swelling than those that received only Nd:YAG irradiation.

Current safety standards for lasers operating in the 1400 to 10,000 nm wavelength region are based on few observations at specific wavelengths using in vivo models that may not represent an accurate correlation to human integument. Based on experimental results conducted with Yorkshire pigs, these standards may not accurately reflect the potential for laser injury when humans are exposed to these wavelengths. It is our belief that one of the primary damage mechanisms involved in these laser injuries is due to energy absorption by skin pigmentation, or melanin. Qualitatively, Yorkshire pigs lack melanin in their skin when compared to a more highly pigmented animal, such as the Yucatan minipig. It is hypothesized that the Yucatan minipig is a more appropriate model for pigmented human skin. By comparing histologic samples taken from various locations on Yucatan minipigs and Yorkshire pigs, and comparing these to potential locations of skin exposure on humans, we present a discussion for the establishment of more appropriate locations for in vivo laser exposure studies.

The absence of verbal feedback, available from most human patients, is a major limitation in veterinary diagnosis in general and in the evaluation of ophthalmic lens opacity in particular. A novel compact dynamic light scattering (DLS) instrument, developed at NASA, offers significant mitigation to this limitation. It not only yields objective repeatable non-invasive estimation of lens opacity but also provides insight into the nature of chemical and physical alternations in the lens and other eye structures. For example, DLS measurements of the cataractous lens may be interpreted in terms of alpha crystalline protein size. In contrast to most conventional methods, the examination results are numerical and readily accommodate statistical analysis. We present results of DLS measurements in laboratory rabbits with naphthalene induced cataracts, rodents with genetically conditioned hypertension and/or diabetes mellitus; as well as applications of the DLS method in clinical veterinary patients. Use of DLS in examination of phacoemulsification fluid, urine and other biological materials, and potential applications in ocular toxically will also be discussed.

Photodynamic therapy (PDT) is a treatment option for several forms of human cancer, and like traditional chemotherapy and ionizing radiation therapy, PDT alone is not curative for some cases. Recent efforts have aimed at developing strategies for adjuvant therapy for PDT. Given the nature of PDT-mediated cell damage, immunotherapy is a promising adjuvant for long-term control of solid tumors. A candidate immune stimulant for use with PDT is monophosphoryl lipid A (MLA), a non-toxic fraction of the endotoxin molecule. The hypothesis is that adjuvant MLA immunotherapy with PDT will improve local tumor control and prevent growth of subsequently implanted tumor cells when compared to PDT alone. To date, no significant differences in circulating leukocyte populations or tumor infiltrating lymphocyte populations have been identified in 9L tumor-bearing F344 rats after systemic administrations of MLA. Likewise, no significant difference has been identified in local tumor control following PDT of 9L tumors with or without adjuvant MLA. Further results are pending.

The use of chromophore dyes to enhance the bactericidal effect of laser energy was studied as a means to optimize laser treatment for the decontamination of wound. Using an in vitro study, various concentrations of indocyanine green (ICG), carbon black, and fluorescein were mixed with a suspension of bacteria and plated on tryptic soy agar. Plates were exposed to a laser beam of 10-15 watts for times ranging from 0 to 180 seconds, incubated overnight, and colony counts were performed. Bacteria not mixed with chromophore were used as controls. Six bacterial strains encompassing a range of bacterial types were used: Staphylococcus aureau, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus spore suspensions, and Clostridium perfringens. Laser treatment alone had no effect on any of the bacteria. Significant killing of gram-positive bacteria, including spores of Bacillus cereus, was observed only with the use of ICG and diode laser energy. No effect was observed using any of the chromophores on the gram-negative bacteria. The results of this study indicate that successful killing of gram-positive bacteria can be achieved using ICG combined with appropriate laser energy and wavelength. Efforts to enhance the susceptibility of gram-negative bacteria to photothermolysis by laser energy were unsuccessful.

Holmium:YAG laser ablation of thoracolumbar disks in dogs has been shown to be an effective alternative to standard surgical fenestration techniques. Our hypothesis was the Holmium:YAG laser could be equally effective and safe when used to ablate cervical intervertebral disks. Six normal chondrodystrophoid breed dogs were used. A sterile, cleaved, 320 micrometers , low-OH quartz optical fiber was inserted into each needle and the laser activated for 40 s at 2 W mean power and a 15 Hz pulse repetition rate for a total of 80 J. Dogs were observed in pain, neurological deficits, or other complications for 24 weeks. At 24 weeks, dogs were euthanatized and cervical disks collected and placed in 10 percent neutral buffered formalin. Disks were decalcified, sectioned at 5 micrometers , and stained with H and E. No problems were encountered during the procedure except occasional difficulties passing the needle by the shoulder to enter the C_6-7 disk space. No complications, including neurologic deficits or pain were observe during the 24 weeks. Histologic examination revealed varying degrees of necrosis and defects created in the nucleus pulposus by laser irradiation. In some instances there was evidence of mild adjacent annular and bony thermal injury. On the basis of these result, the Ho:YAG laser appears to be a safe and efficacious method for ablation of canine cervical disks.

The use of a 15-watt diode laser (CeramOptec)in 30 surgical procedures in dogs and cats was reviewed. Ease of use, operator safety, hemostasis control, wound healing, surgical time, complication rate, and pain control were observed and recorded. Procedures performed were partial pancreatectomy, nasal carcinoma ablation, medial meniscus channeling, perianal and anorectal mass removal (5), hemangioma and hemangiopericytoma removal from two legs, benign skin mass removal (7), liver lobectomy, partial prostatectomy, soft palate resection, partial arytenoidectomy, partial ablation of a thyroid carcinoma, photo-vaporization of the tumor bed following malignant tumor resection (4), neurosheath tumor removal from the tongue, tail sebaceous cyst resection, malignant mammary tumor and mast cell tumor removal. The laser was found to be very simple and safe to use. Hemostasis was excellent in all but the liver and prostate surgeries. The laser was particularly effective in preventing hemorrhage during perianal, anal, and tongue mass removal. It is estimated that a time and blood loss savings of 50% over that of conventional surgery occurred with the use of the laser. All external wounds made by laser appeared to heal faster and with less inflammation than those made with a conventional or electrosurgical scalpel.

Videoendoscopy has truly enlarged the scope of diagnostic and therapeutic gastroenterology. However, videoendoscopic examinations are limited to the mucosal surface. Endoscopic ultrasound allows the endoscopist a view beyond the intestinal wall which opens the door to a variety of new gastroenterologic techniques. The evaluation of plain images in combination with contrast-enhanced imags has been found to be helpful when applied to CT and MRI. A similar advantage may be found for endoscopic ultrasound (EUS) studies. The efficacy of EUS with and without contrast enhancement is critically reviewed.

Enhanced endoscopic detection of small flat adenomas is becoming increasingly important as they have a reported 14 percent incidence of dysplasia when compared with 5% incidence in polypod adenomas of the same size. These lesions even when invasive do not show up against the translucent surrounding mucosa making endoscopic detection difficult. Dye spraying with indigo carmine makes their morphology clear, with well-circumscribed borders. Dye spraying and magnifying endoscopes can be used to observe pit patterns on the surface of the bowel. Combining dye spraying and high-resolution video endoscopy demonstrates well the colorectal epithelial surface. Scanning immersion video endoscopy visualizes the epithelial surface of the colorectal mucosa by high-resolution endoscopy after filling the lumen with water. Endoscopic ultrasound can be used to see if the lesion is intramucosal or not and assess the depth of invasion if malignancy is presented. Laser induced fluorescence spectroscopy has the potential to detect colonic dysplasia in vivo. Combining such technologies with conventional colonoscopy can help in the surveillance of large areas of colonic mucosa for the presence of dysplasia. Guided biopsy can replace random biopsy based on information provided at the time of colonoscopic examination.

We have developed a new device to effectively and quickly stop bleeding. The new device uses a small, 5 W diode laser to heat-up the tip of a modified medical forceps. The laser beam is totally contained within a protective enclosure, satisfying the requirements for a Class I laser system, which eliminates the need to protective eyewear. The new device is used in a manner similar to that of a bipolar electrocautery device. After visual location, the bleeding site or local vessel(s) is grabbed and clamped with the tips of the forceps-like instrument. The laser is then activated for a duration of typically 5 sec or until traditional visual or auditory clues such as local blubbling and popping indicate that the targeted site is effectively cauterized. When the laser is activated, the tip of the instrument, thus providing hemostasis. The new device was evaluated in animal models and compared with the monopolar and bipolar electrocautery, and also with the recently developed ultrasound technology. It has new been in clinical trials for abdominal surgery since September 1997.

Mucosal incision technique by diode laser ablation was studied to ensure the operation of endoscopic mucosal resection (EMR), which is gold standard method for early gastric cancer with little/no risk of lymphnode metastasis. Our method was designed to facilitate grasping a large lesion by hitching the snaring wire on the incised mucosal groove around the lesion. We employed local submucosal injection of indocyanine green (ICG) solution. ICG solution was used to prevent direct laser light penetration to the muscularis propriae owing to strong absorption of 805nm light (absorption coefficent at 805 nm is about 200cm^-1). We used diode laser radiation with an output of 25W by contact (0.1, 0.5, 1.0 kg/cm²) and non-contact irradiation methods. In the preliminary experiment with resected porcine stomach, muscularis propriae was intact by the 60s non-contact irradiation or the 8s contact irradiation with contact pressure of 1kg/cm². In the endoscopic experiment we used 3 dogs. Using conical contact probe, we successfully demonstrated 3cm diameter circular incision with sharp groove in 10 minutes. We could place the snaring wire on the incised groove. Histology of the endoscopically incised canine stomach revealed that the submucosal layer welled up to 6mm in thickness and the bottom of the incision groove reached 1.9mm at deepest below the mucosal muscle. The thickness of the coagulation layer around the incised groove was up to 1.8mm. No damage was seen a the muscularis propriae. We demonstrate easy as well as sure snaring by using our laser incision technique. We think our technique may be available to enhance the efficacy of EMR for early gastric cancer including the lesion over 2cm in diameter.

We have demonstrated that when using in surgical operations the radiation of YAG:Nd laser with 1.44 μm wavelength exhibits better cutting capabilities as compared to the same laser at 1.32 μm wavelength. The laser scalpel at 1.44 μm also provides adequate hemostasis at non-typical section of parenchymals without blood vessel ligation, however this capability is higher for 1.32 μm radiation. It is possible to combine the advantages of both radiations by repetitive switching the laser between two wavelengths or mixing two simultaneously generate wave in one optical waveguide. Application of several YAG:Nd laser wavelengths with different absorption coefficients in a single operation on the soft tissue allows one to coagulate large-scale blood vessels and to minimize thermal damages of surrounding tissue.

Fluorescence excitation spectra of skin have been determined to be stable and reproducible. Three major bands dominate the wavelength range 280-400 nm. The major epidermal band due to tryptophan moieties appears at 295±5 nm and the major dermal bands due to collagen cross links appear at 335±5 nm and at 370±5 nm. The tryptophan fluorescence intensity has been found to increase with exposure to UV radiation; the UVB wavelengths are more effective than the UVA wavelengths. The PDCCL fluorescence intensity has been found to decrease dramatically with exposure to UVA in a wavelength specific way. The maximum of the action spectrum for this process is centered at the maximum of the excitation spectrum. The fluorescence of the skin recovers within 24 hours following exposure to UVA from single exposures. Multiple exposures produce permanent changes, in a follow-up of 8 weeks. the changes in the tryptophan fluorescence are probably due to changes in the molecular environment brought about by changes in the electrolyte balance in the epidermis following exposure. The changes in the dermis following UVA exposure appear to be associated with change in the collagen cross links, either through their association with other dermal species leading to quenching of the fluorescence or by the formation of stronger cross links with a smaller quantum efficiency. As these changes are immediate both alterations may provide the means for in vivo UV dosimetry.

Clinical diagnosis of acute otitis media (AOM) in children is not easy. It was assumed that there is a difference ΔT between the Tympanic Membrane (TM) temperatures in the two ears in unilateral AOM and that an accurate measurement of ΔT may improve the diagnosis accuracy. An IR transmitting fiber, made of AgClBr, was coupled into a hand held otoscope and was used for the non-contact (radiometric) measurements of T_T, the TM temperature. Experiments were carried out, first, on a laboratory model that simulated the human ear, including an artificial tympanic membrane and an artificial ear canal. Measurements carried out using commercially available tympanic thermometers shown that the temperature T_c of the ear canal affected the results. T_c did not affect the fiberoptic radiometer, and this device accurately measured the true temperature, T_T of the tympanic membrane. A prospective blinded sampling of the TM temperature was then performed on 48 children with suspected AOM. The mean temperature difference between the ears, for children with unilateral AOM was ΔT = (0.68 ± 0.27)°C. For children with bilateral AOM it was ΔT = (0.14±0.10)°C (p<0.001). It was demonstrated that afor unilateral AOM the difference ΔT was proportional to the systemic temperature. In conclusion, the fiberoptic interferometric measurements of the TM can be a useful non-invasive diagnostic tool for AOM, when combined with other data.

More than 2 500 leg veins patients were treated with dye laser / ScleroPlus, Candela, USA / successfully in our clinic and we use this therapy as the basic cosmetics treatment. But especially diameter of leg vein is limiting factor. Very often we have to treat some cases that are not ideal for classical surgical or for dye laser method. We decided to make invasive perivenous laser coagulation. We adapted original Czech 1064/1319 nm Nd:YAG laser / US patent pending /, which is new combine tool, for invasive application. Principe: After we have penetrated the cutis with laser fiber we coagulate leg veins during slowly perivenous motion. Perfect preoperative examination is a condition of success. After 15 months we have very interesting results. Some patients / 15%/ were perfect treated only with this possibility but excellent results are acquired from combination with dye laser.

Endoscopic ultrasound (EUS) is a technology that had been used primarily as a passive imaging modality. Recent advances have enabled us to move beyond the use of EUS solely as a staging tool to an interventional device. Current studies suggest that interventional applications of EUS will allow for minimally invasive assessment and therapies in a cost-effective manner. Endoscopic ultrasound with fine needle aspiration (EUS-FNA) has been demonstrated to be a technically feasible, relatively safe method of obtaining cytologic specimens. The clinical utility of EUS- FNA appears to be greatest in the diagnosis and staging of pancreatic cancer and in the nodal staging of gastrointestinal and pulmonary malignancies. In addition, EUS-FNA has demonstrated utility in the sampling pleural and ascitic fluid not generally appreciated or assessable to standard interventions. Interventional applications of EUS include EUS-guided pseudocyst drainage, EUS-guided injection of botulinum toxin in the treatment of achalasia, and EUS- guided celiac plexus neurolysis in the treatment of pancreatic cancer pain. Finally, EUS-guided fine-needle installation is being evaluated, in conjunction with recent bimolecular treatment modalities, as a delivery system in the treatment of certain gastrointestinal tumors.

Our precise in vivo investigations examined various laser choices for TMR including Ho:YAG, CO₂ and XeCl excimer laser. These studies have revealed that among the three lasers tested, the XeCl excimer ablation produces the least tissue damage. In this study we have further examined the use of the excimer laser for optical application in TMR. To this end, myocardial ablation was conducted in vivo in a porcine model with the use of multiple fiber catheters of 1.0mm and 1.4mm in diameter. During ablation, the catheters were advanced into the myocardium at different constant speeds via a specially designed electromechanical device. Each of the catheters was tested at 35 mJ/mm² and different pulse repetition rate. Optimal operating parameters were defined as those that produced the most uniform tissue ablation, and the least thermal and shock- wave damage as determined via computerized histopathological analysis. We have found that ablation rate, pulse repetition rate, catheter size, and catheter advancement speed are parameters closely intertwined and crucial to the histological outcome of TMR. Within the values of parameters tested, larger catheters, pulse repetition rates between 35 and 40 Hz, and advancement speeds of about 1.3 mm/s (~0.05 inches/s) seem to provide reasonably optimized parameters for excimer-based TMLR.

Laser treatment of the prostate as an alternative for transurethral resection of the prostate (TURP) has evolved from a complicated troublesome procedure to a single office procedure. In this study, we compared the efficacy of different electrosurgical and laser techniques. The data of seven prospective studies in 280 patients were evaluated. The patients were treated for bladder outlet obstruction due to benign prostatic hyperplasia during the period from 1992 until 1998. Five procedures were offered using Nd:YAG laser light, including ultrasound-guided free beam, a free beam technique applying either a predetermined energy dose or a visually-guided energy does, contact laser prostatectomy and a hybrid method where free beam coagulation was followed by contact laser. Two procedures were offered using electrosurgery comprising transurethral resection and transurethral electrovaporization. The clinical outcome was assessed pre-operatively and 6 months post-operatively by free flowmetry, post-void residual, and Shaeffer obstruction grade. Results after 6 months are shown in the table below.

Purpose: Laser interstitial thermotherapy is a promising minimally- invasive technique for the treatment of small cancers of the breast that are currently removed surgically lumpectomy. The purpose of this work was to analyze in situ temperature fields recorded with stainless-steel thermocoupled probes during experimental laser interstitial thermo-therapy (LITT). Methods: Both a CW Nd:YAG laser system emitting 20W for 25 to 30s and a 980 nm diode laser emitting 10 to 20 W for up to 1200s delivered through a fiber-optic probe were used to create localized heating in fatty cadaver pig tissue and milk as phantoms. To quantify an artifact due to direct heating of the thermocouple probes by laser radiation, experiments were also performed in air, water and intralipid solution. The temperature field around the fiber-optic probe during laser irradiation was measured every 0.3 s or 1 s with an array of up to fifteen needle thermocoupled probes. The effect of light absorption by the thermocouples probes was quantified and the time-dependence of the temperature distribution was analyzed. Results: After removal of the thermocouple artifact, the temperature was found to vary exponentially with time with a time constant of 600 to 700 s. Conclusions:The time-dependence of the interstitial temperature can be modeled by exponential functions both during ex vivo and in vivo experiments.

Temperature increases and the resultant thermal field produced by the irradiation of ex vivo (porcine and human) and in vivo (porcine) tissue models appropriate to the treatment of human breast tissue using Nd:YAG (cw:60W) radiation delivered with an interstitial fiber optic probe were recorded with an array of fifteen 23 gauge needle thermocouple probes connected to a laboratory computer based data acquisition system. Using a stepwise decreasing power cycle to avoid tissue charring, acceptably symmetric thermal fields of repeatable volumetric dimensions were obtained. Reproducible thermal gradients and predictable tissue necrosis without carbonization could be induce din a three centimeter diameter region around the fiber probe during a single treatment lasting only 3 minutes. The time-dependence of the temperature rise of the thermocouples surrounding the LITT probe were quantitatively modeled with simple linear functions during the applied laser heating cycles.

Carcinoma of the breast continues to be the second major cause of death in women in the US today, with 180,000 new cases detected annually in the US. One third of these carcinomas are 1 cm in size or less. The current techniques of surgical resection require operating rooms, anesthesia, cosmetic concerns and cost. The benefits of cryosurgery for the treatment of visceral tumors has stimulated the investigation of this approach for carcinomas of the breast. Here within is a work-in-progress report of our research program to evaluate a cryodevice and techniques for breast cryosurgery.

Fourier transform IR fiberoptic evanescent wave (FTIR-FEW) spectroscopy has been suggested as a powerful tool for clinical diagnostics of normal, pre-cancerous, and cancerous breast tissue ex vivo and in vitro in the middle IR region of the spectrum(850-1850 cm^-1). This method is suitable for noninvasive and direct measurements of the spectra of normal and pathological tissues in vitro, ex vivo and in vivo. For the first time this method has been use nondestructively, rapidly, fast (15-20 sec) and remotely in the operating rooms of clinics. The aim of our studies has been the on-line testing of various tumor tissues during surgery to optimize and localize an area to remove tissue. We measured very small samples of normal and malignant breast tissue ex vivo with a fiber bent to a special angle, forming a special tip probe configuration. We also suggest here the minimally invasive FTIR-FEW diagnosis tool using 'needle' changeable tip probe for biopsy applications. The corresponding spectral histopathology scheme could be developed with help of this technique in vitro. The breast tissue at different stages of tumor or cancer has been distinguished very clearly in spectra of amide, cyclic and non-cyclic hydrogen bonded fragments, phosphate groups and sugars.

This study explores the feasibility of image directed laser ablation of breast tumors as an alternative to traditional surgery. A series of 22 treatments were performed in 12 patients. The cancers were targeted with pre- and post- gadolinium enhanced RODEO breast MRI. 18 g MRI compatible needles were stereotaxically placed with RODEO breast MRI guidance. Laser ablation was implemented with a diode laser (805 nm) at 3 watts of power for about 500 seconds. The treatment was performed interactively with dynamic RODEO MRI control. The treatment zone was manifested as a hypointense zone on the dynamic images. The needle or treatment duration can be adjusted during the course of the ablation depending upon the location of the tumor and hypointense zone. In all cases correlation with conventional surgical excision with serial sectioning of the specimen was performed. PCNA stains of the treatment zone was used to confirm effective ablation and correlate the treatment zone size with the hypointense zone demonstrated on MRI. This study demonstrates the potential for RODEO breast MRI as an effective method for coordinating the interactive deliver of laser ablation in the treatment of breast cancer.

Computer-aided detection of breast cancer in screening mammography is just now becoming a clinically useful tool for radiologist. Systems are being implemented to act as second readers of mammograms. These systems automatically detect suspicious regions in digitized films, or directly acquired digital images, then prompt the radiologists to examine the identified regions more carefully. The purpose of using a computerized system as a second reader is to reduce the chances of overlooking visible signs of malignancies and hence improve the breast cancer detection rates in screening programs. This paper present an overview of a mammogram image analysis system developed at Intelligent Systems, M.D., Inc. for identifying all primary signal of cancer in mammogram images. The system has been tested on a set of 88 mammography cases of four views each. The cases contain a total of 96 malignant abnormalities. They system currently achieves 91 percent sensitivity at an average of just over one false prompt per image. Ongoing system refinement and updates are expected to further improve performance.

To bring the current laboratory and feasibility studies to successful, focused clinical trials, several important considerations must be met. These include tumor selection, patient selection, treatment method, assessment of the treatment field, and short and long term clinical strategies.

Near-infrared confocal reflectance microscopy (CM) provides non- invasive real-time images of thin en-face tissue sections with high resolution and contrast. Imaging of cells, nuclei, other organelles, microvessels, and hair follicles has been possible at resolution comparable to standard histology, to a maximum depth of 250-300 μm in human skin in vivo. We have characterized psoriasis as a prototype of benign proliferative skin conditions, and non-pigmented skin malignancies in vivo based on their unstained, native histologic features using CM. Our data shows that reflectance CM may potentially diagnose and morphometrically evaluate proliferative skin lesions in vivo.

At present nobody doubts the advantages of minor laser surgery over the conventional one.Bloodless manipulations, ablation, minor injury to the tissues while using laser equipment ensures its wide application in such fields as dermatology and cosmetology, especially since the semiconductor lasers because available at the technological market. No doubt CO₂ and solid laser are still playing an important role, however, their imperfect fiber optic qualities limit their use in these field,s where advantages of diode lasers with flexible and fine quartz-polymeric optical fiber are obvious. The elaboration of new diode surgical lasers made it possible to invent new surgical equipment for solving many medical problems in the optimal way. Application of contact and noncontact laser methods in dermatology, gynecological plastic surgery and otolaryngology is discussed. A combined use of these methods demonstrates a positive effect on therapy results and healing time.