bluuebunny/crossref_metadata_2025 huggingface dataset:
Ablation of bone and polymethylmethacrylate by an XeCl (308 nm) excimer laser
Authors: Yow Lindy , Nelson J. Stuart , Berns Michael W.
Published: March 2007

One of the main problems in orthopaedics is the surgical removal of hard substances, such as bone and polymethylmethacrylate (PMMA). Such materials are often very difficult to remove without mechanical trauma to the remaining tissue. This study investigated the feasibility of the ultraviolet 308 nm excimer laser in the ablation of these materials. The beam was delivered through a 1 mm‐diameter fiber optic at 40 Hz with energy densities at the target surface of 20–80 J/cm2 per pulse.

The goal of the study was to establish the ideal dosimetry for removing bone and PMMA with minimum trauma to the adjacent tissue. Histology revealed that the 308 nm laser effectively removed bone leaving a thermal damage zone of only 2–3 μm in the remaining tissue. Increasing the energy per pulse gave correspondingly larger and deeper cuts with increasing zones of thermal damage. The excimer laser was also effective in the ablation of PMMA, creating craters in the substrate with a thermal damage zone of 10–40 μm. The debris from both substrates was evaluated.
Parameters affecting laser palliation in patients with advanced digestive cancers
Authors: Brunetaud Jean Marc , Maunoury Vincent , Cochelard Dominique , Boniface Brigitte , Cortot Antoine , Paris Jean Claude
Published: March 2007

Ninety‐nine nonsurgical patients (group I) with esophagogastric cancer were referred to the laser center for palliation of dysphagia, and another 142 nonsurgical patients (group II) with a rectosigmoid cancer were referred for palliation of abnormal rectal discharge (125 patients) or occlusion (17 patients). The immediate success rate was 83% in group I and 90% in group II. Patients were retreated monthly. The average duration of palliation was 4.3 months ± 0.5 (± standard error) in group I and 9.3 months ± 0.95 in group II. Complication rate was 4% in group I and 3.4% in group II. Parameters affecting results were found only in group I. Factors that could negatively affect the immediate success rate included annular size of the tumor basis more than two thirds of the circumference, tumor localization at the upper third of the esophagus, and recurrence after a nonlaser treatment. The average duration of improvement after initial success was affected only by the circumferential extension.
Fatal air embolism as a complication of laser‐induced hyperthermia
Authors: Schröder Tom M. , Puolakkainen Pauli A. , Hahl Juha , Rämö O. Juhani
Published: March 2007

Laser‐induced hyperthermia is a new treatment modality for malignancies. When large tumors are treated with laser thermia, relatively high laser powers (4–6 W) must be used to accomplish destruction of the cancerous cells. Overheating and burning of the laser fibers and contact tips during laser thermia treatment must be prevented by using coaxial gas or fluid flow. The present report describes a case of fatal air embolism as a complication of laser thermia using coaxial gas. The authors warn all surgeons performing this procedure not to use coaxial air flow for cooling the contact tips because of the potential risk of air embolism.
Correlation of fluorescence emission with the plaque content and intimal thickness of atherosclerotic coronary arteries
Authors: Gaffney Edward J. , Clarke Richard H. , Lucas Alexandra R. , Isner Jeffrey M.
Published: March 2007

The use of fluorescence emission for guidance during laser angioplasty may be limited by the complexity of the emission from the broad range of atherosclerotic plaques normally encountered in diseased coronary arteries. Fatty, fibrous, and calcific plaque content as well as maximal intimal thickness were measured and correlated with fluorescence intensity ratios from the emission spectra for a broad cross‐section of atherosclerotic plaques from human necropsy specimens. Multiple and stepwise regression analysis was used to analyze intensity ratios of 13 wavelengths between 390 and 600 nm corresponding to regions of observed spectral structure. The level of correlation of the intensity ratios with fatty and calcific plaque content was found to be dependent on the complexity of the atherosclerotic lesion. The fluorescence emission was found to correlate well with both fibrous plaque content and intimal thickness, allowing the differentiation between normal and atherosclerotic samples. In conclusion, plaque characteristics can be assessed by fluorescence emission, although the successful implementation of spectroscopic guidance is dependent on the level of prediction error which may vary with tissue type.
In vitro comparison of thulium‐holmium‐chromium:YAG and argon ion lasers for welding of biliary tissue
Authors: Oz Mehmet C. , Bass Lawrence S. , Popp Howard W. , Chuck Roy S. , Johnson Jeffrey P. , Trokel Stephen L. , Treat Michael R.
Published: March 2007

Laser welding offers several potential advantages over suture closure, including improved healing, lack of a nidus for stone formation, and greater speed and ease. We examined in vitro gallbladder cystic duct welds created by two different systems, the thulmium‐holmium‐chromium (THC):YAG (2,150 nm) and argon ion (488–514 nm) lasers, in an effort to define suitable parameters for tissue fusion. Mean bursting pressures for argon welds were 95 mm Hg at 1.5 W CW and 26 mm Hg at 1.5 W, 50 msec chopped delivery. For the THC:YAG laser, the mean bursting pressure for welds created with 300 mJ pulses was 45 mm Hg. Full‐thickness tissue fusion and limited collateral thermal damage were observed histologically for both the CW argon and pulsed THC:YAG welds. Examination of the suggested mechanisms of tissue fusion for these photothermal lasers suggests that increased duration of tissue heating at the appropriate temperature results in more extensive collagen crosslinking and a stronger weld.
Evaluation of a smoke evacuator used for laser surgery
Authors: Smith Jerome P. , Moss C. Eugene , Bryant Charles J. , Fleeger Alan K.
Published: March 2007

A preliminary study was conducted to determine the effectiveness of a smoke evacuation system used in laser surgery. A 30 W medical CO2 continuous wave (CW) laser was used to make cuts in a pork chop to simulate smoke production during laser surgery. A commercially available smoke evacuation system was used to control the smoke from the simulated surgery. The smoke concentration was measured at 6 in and at 3 and 4 ft from site of laser interaction. The nozzle of the smoke evacuator was located at distances of 2, 6, and 12 in from the surgical site to measure the relative effectiveness of the control. Complete control of smoke was achieved when the nozzle was located at 2 in, but significant amounts of smoke escaped when the nozzle was located at 6 and 12 in. Suggestions for the use of the smoke evacuation system and areas for further study are given.
Experimental studies of the application of the Er:YAG laser on dental hard substances: II. Light microscopic and SEM investigations
Authors: Keller Ulrich , Hibst Raimund
Published: March 2007

Many studies have been undertaken trying to use various laser systems as optical drills on dental enamel and dentin, but the high radiant exposure needed and subsequent high temperature rises lead to fractures of the hard substances and possible damages to the pulp. Compared to the other laser systems, the use of the Er:Yag laser has given encouraging results. Optical and scanning electron microscopy showed only minimal if any damage of the surrounding tissue.
Visible action spectrum for melanin‐specific selective photothermolysis
Authors: Margolis Randall J. , Dover Jeffrey S. , Polla Luigi L. , Watanabe Shinichi , Shea Christopher R. , Hruza George J. , Parrish John A. , Anderson R. Rox
Published: March 2007

The skin of black and albino guinea pigs was irradiated with single, 750 nsec‐long laser pulses at 435, 488, 530, and 560 nm in order to determine an action spectrum for the gross threshold response of immediate epidermal whitening. In addition, the immediate and delayed gross and histologic changes induced at, above, and below the threshold radiant exposures at all four wavelengths were studied. The action spectrum in the black guinea pigs was consistent with the reported absorption spectrum of DOPA‐melanin. Histologically, there was epidermal damage immediately after radiant exposures at and above threshold at all four wavelengths. In addition, radiant exposures greater than threshold caused an immediate decrease in stainable epidermal pigment that was most marked at 435 and 488 nm. The healing response was also wavelength‐ and dose‐dependent. Seven days after above‐threshold exposures, there was little epidermal pigment in the 435 nm specimens. As wavelength increased, there was progressively more pigment, and in the 560 nm specimens, the epidermal pigment was equivalent to that seen in nonirradiated black guinea pig control specimens. Seven days after subthreshold radiant exposures, there was increased epidermal pigmentation and melanocytes at all four wavelengths. This was the most pronounced in the 435 nm specimens. There was no observable epidermal damage in albino guinea pig skin.
Comparative study of the “point‐by‐point technique” and the “scanning technique” for laser treatment of port‐wine stain
Authors: Mordon Serge R. , Rotteleur Guy , Buys Bruno , Brunetaud Jean Marc
Published: March 2007

Photocoagulation using the argon laser has been proven to be an effective method for the treatment of port‐wine stains (PWS). However, it is very difficult to reproduce the parameters of laser treatment. This leads to inaccurate energy dosages secondary to the difference in treatment patterns. The aim of this study was to compare the conventional point‐by‐point technique (PT) for PWS treatment against a new scanning technique (ST) using a device called “Hexascan” (PREIN & Partners, Ferney‐Voltaire, France). A total of 249 patients (171 females and 78 males) using the argon laser have been studied in a retrospective study. Clinical results are presented.

For each technique, blanching and hypertrophic scarring were examined. The results are classified into two groups: satisfactory and unsatisfactory. The clinical results show that the ST with the Hexascan is superior to the conventional PT. Scarring is drastically reduced because overdosage and overheating are avoided. Because of precisely controlled spot patterns, quality and homogeneity of blanching is improved. Treatment time can be reduced to 20% of that of the PT.
Cytotoxicity and mutagenicity of excimer laser radiation
Authors: Kochevar Irene E.
Published: March 2007

Excimer laser radiation at 193 nm, 248 nm and 308 nm cause DNA photochemistry. The photobiological effects resulting from exposure of cells to 308 nm and 248 nm radiation appear to be the same as those obtained using low irradiance CW sources at similar wavelengths. This indicates that the high irradiances available from the excimer laser cause the same DNA photochemistry as the lower‐irradiance CW sources. Excimer laser radiation at 193 nm causes less cytotoxicity than predicted based on the DNA absorption spectrum. This may result from absorption of 193 nm radiation by protein present between the cell surface, and nuclear DNA, or from less efficient DNA photochemistry using 193 nm radiation. In vitro assays indicate that DNA‐damaging effects resulting in cytotoxicity decrease in the order 248 nm > 308 nm > 193 nm.
Macrophage responsiveness to light therapy
Authors: Young Steve , Bolton Peter , Dyson Mary , Harvey Wil , Diamantopoulos Costas
Published: March 2007

Macrophages are a source of many important mediators of wound repair. It was the purpose of this study to see if light could stimulate the release of these mediators.

In this study an established macrophage‐like cell line (U‐937) was used. The cells were exposed in culture to the following wavelengths of light: 660 nm, 820 nm, 870 nm, and 880 nm. The 820‐nm source was coherent and polarised, and the others were non‐coherent. Twelve hours after exposure the macrophage supernatant was removed and placed on 3T3 fibroblast cultures. Fibroblast proliferation was assessed over a 5‐day period.

The results showed that 660‐nm, 820‐nm, and 870‐nm wavelengths encouraged the macrophages to release factors that stimulated fibroblast proliferation above the control levels, whereas the 880‐nm wavelength either inhibited the release of these factors or encouraged the release of some inhibitory factors of fibroblast proliferation.

These results suggest that light at certain wavelengths may be a useful therapeutic agent by providing a means of either stimulating or inhibiting fibroblast proliferation where necessary. At certain wavelengths coherence is not essential.
Alteration of spectral characteristics of human artery wall caused by 476‐nm laser irradiation
Authors: Chaudhry Hina W. , Richards‐Kortum Rebecca , Kolubayev Tatiana , Kittrell Carter , Partovi Firooz , Kramer John R. , Feld Michael S.
Published: March 2007

Fluorescence spectroscopy is a promising new technique for discrimination of normal and atherosclerotic arterial tissues. It has been suggested that this technique be used as a guidance system for laser angiosurgery catheters; however, irradiation by 476‐nm light can change the spectroscopic properties of arterial tissue. We present studies that establish intensity levels and exposure times at which alterations in tissue spectral properties are minimal. We also investigate the nature of spectral alterations following exposure of normal human aorta to high intensities of 476‐nm laser light. Changes in laser‐induced fluorescence (LIF) are characterized by two prominent features: the peak fluorescence intensity decreases permanently, and the fluorescence lineshape changes in a largely reversible way. We relate these changes to alterations in individual tissue chromophores: permanent changes in absolute fluorescence intensity are due to irreversible changes in tissue fluorophores, reversible changes in fluorescence lineshape are due alterations in tissue absorbers. A simple kinetic model is used to describe the decrease in absolute fluorescence intensity.
Does low‐Intensity helium‐Neon laser irradiation alter sensory nerve active potentials or distal latencies?
Authors: Basford J. R. , Daube J. R. , Hallman H. O. , Millard T. L. , Moyer S. K.
Published: March 2007

The effect of 1 mW helium neon continuous‐wave (0.633 μm) laser irradiation on superficial radial sensory and median sensory nerve function was examined in a double‐blind, controlled study involving 40 volunteers. No differences in action potential amplitudes, distal latencies, or forearm skin temperatures were found between the treated and control groups either at the time of irradiation or at subsequent evaluations 15 and 30 minutes later. As a result, we are unable to confirm reports that low‐energy lasers of this power and wavelength alter nerve function.
Laser recanalization in high risk patients
Authors: Seeger James M. , Kaelin Lawrence D. , Barbeau Gerald , Abela George S.
Published: March 2007

Laser recanalization was attempted in 13 patients in whom the risk of surgical therapy was increased by severe angina, infection, absent venous conduit, or recent deep venous thrombosis, and in 4 patients at high risk for limb loss due to severe infrapopliteal arterial occlusive disease. Total occlusions of the superficial femoral, tibial, or peroneal arteries were treated. Recanalization was accomplished using Argon laser power and a Spectraprobe‐PLRm. Two patients also required common femoral artery endar‐terectomy to improve inflow. Laser recanalization was successful in 9 patients (53%), and 8 (47%) had relief of symptoms. None of the 4 patients with tibial and peroneal artery occlusion had successful recanalization or limb salvage. Restenosis or reocclusion developed in 4 patients during the first year after successful recanalization, but only 1 had recurrent symptoms. Limb salvage was initially achieved in 5 of 8 recanalization failures by surgical reconstruction but 3 developed graft infections requiring graft removal in 2 and amputation in 1. Thus, laser recanalization can accomplish limb salvage in selected patients whose medical or surgical risks complicate arterial bypass surgery.
Photodynamic therapy: Tumor volume limitation and tumor response for murine fibrosarcoma
Authors: Al‐Watban Farouk A. H.
Published: March 2007

The clonogenic survival rates and tumor growths following photodynamic therapy (PDT) were studied as a function of tumor volume for RIF‐1 using C3H mice as an animal model. The clonogenic survival rates showed a saturation level approaching a 99.8% survival rate for large volumes (above 1,900 mm3), possibly indicating poor light utilization of 630 nm because of the limited tissue penetration and/or tumor hypoxia. With a small tumor volume [<150 mm3], the survival rate (<0.3%) showed an exponential increase with volume. The survival rates (<0.03%) corresponding to a volume lower than 50 mm3 gave complete tumor eradication. On the other hand, partial response and recurrence were noticed with volumes larger than 90 mm3, which had more than ∼0.1% survival rates. After PDT, all tumors responded with immediate swelling and skin discoloration, followed by necrosis, tumor delay, and regrowth. Regrowth rate and tumor cell doubling time were slower than the control growths and decreased further following superficial irradiation with a second interstitial illumination. The regrowth rates were slow for small initial tumor volumes and fast for large initial tumor volumes. Also, the delay period was longer for the small initial tumor volumes in comparison to a shorter period for the medium tumor volumes and very low probability of delay for the large volumes.
Sutureless End‐to‐End bowel anastomosis using Nd:YAG and water‐soluble intralurninal stent
Authors: Costello Anthony J. , Johnson Douglas E. , Cromeens Douglas M. , Wishnow Kenneth I. , Von Eschenbach Andrew C. , Ro Jae Y.
Published: March 2007

Sutureless end‐to‐end intestinal anastomoses were successfully constructed in 20 rabbits. A water‐soluble intraluminal stent was used to approximate the tissue edges, and the anastomotic seam was lased with 1.06 μm neodymium:YAG (Nd:YAG) laser energy supplied through a hand‐held 600‐μm gas‐cooled noncontact optical fiber. A continuous 5‐watt wave of power was applied over periods ranging from 46 to 92 seconds to produce the tissue blanching and shrinkage that indicated a satisfactory tissue weld. Integrity, degree of tissue reaction, and bursting pressures of the anastomoses were compared to those of anastomoses constructed using standard sutured techniques.

The results of the two methods were equivalent at 1 to 3 days, but the laser‐fused enteric anastomoses showed less inflammatory reaction and greater bursting pressures at 7 and 14 days. Application of a variety of proteinaceous solutions including extracellular matrix materials and epidermal growth factors prior to lasing failed to augment wound healing. We conclude that lasers show promise as reconstructive, in addition to ablative, surgical instruments.
Laser photobioactivation mechanisms: In vitro studies using ascorbic acid uptake and hydroxyproline formation as biochemical markers of irradiation response
Authors: Labbe Robert F. , Skogerboe Kristen J. , Davis Holly A. , Rettmer Rebecca L.
Published: March 2007

Clinical investigations of laser photobioactivation, or biostimu‐lation, might be differently designed and more fruitful if knowledge of basic biochemical mechanisms were better understood. In this investigation, biochemical events identified as responses to 904 nm irradiation included increased ascorbic acid uptake by fibroblasts. These cells also showed increased hydroxyproline formation, and this was increased several‐fold by the addition of proline to the medium. Maximum biochemical responses were observed at a pulse frequency of 67 Hz and a pulse width of 150 nsec with an energy density of approximately 7 mJ/cm2 per exposure. Elements in the mitochondrial cytochrome system are proposed as the radiation absorbing chromophore(s). Hypothet‐ically, the energy generated is linked to ascorbic acid uptake, which in turn stimulates collagen synthesis.
Study of the mechanisms of laser‐induced release of liposome‐encapsulated dye
Authors: Khoobehi Bahram , Char Clifford A. , Peyman Gholam A. , Schuele Kathleen M.
Published: March 2007

To differentiate the contributing factors (blood or encapsulated dye) leading to the release of encapsulated dyes from liposomes after laser exposure, we initiated an in vitro experimental study. The release of encapsulated calcein was quantified under various experimental conditions in whole blood and in buffered solution containing high‐density lipoprotein. Generally, the amount of dye release improved with an increase in laser power, with a maximum release of approximately 80% of encapsulated dye. Because the laser exposure was not continuous, only 80% of each sample was actually exposed. Therefore, 80% release may be thought of as total release. In a lipoprotein/buffer mixture, the 488 nm wavelength caused greater dye release than the 577 nm wavelength, because the maximum absorption of calcein is near 488 nm. The laser wavelength at 577 nm, however, caused greater release in the blood mixture, reflecting the peak absorption of hemoglobin at near 577 nm. At a 3x higher liposome concentration, the differences in the effects of wavelengths on the release of dye from liposomes were insignificant. Although the 577 nm wavelength is an optimum wavelength for dye and drug delivery in the presence of blood, the 488 nm wavelength might also be suitable for the release of dye from the liposomes.
Strength of laser vascular fusion: Preliminary observations on the role of thrombus
Authors: Oz Mehmet C. , Bass Lawrence S. , Chuck Roy S. , Johnson Jeffrey P. , Parangi Sareh , Nowygrod Roman , Treat Michael R.
Published: March 2007

We hypothesized that autologous clot deposited on the luminal surface of laser vascular welds immediately after creation would produce higher time zero bursting pressures than could be achieved in welds perfused with saline alone. To test this hypothesis, we compared bursting pressures of welds created in isolated rabbit aortic segments (1) with saline perfusion only, (2) with blood perfusion, and (3) with blood perfusion followed by infusion of urokinase. Tissue welds with saline perfusion had a mean bursting pressure of 159 ± 45 mm Hg; tissue welds following blood perfusion had a mean pressure of 262 ± 29 mm Hg; tissue welds with blood perfusion followed by urokinase infusion had a mean bursting pressure of 187 ± 35 mm Hg. The saline and urokinase groups were not significantly different. However, the blood‐perfused group was significantly higher than both the saline group and the urokinase group. Thus, the addition of urokinase eliminates the beneficial effects noted after blood reperfusion. These observations suggest that the enhancement of weld strength following exposure to blood is due predominantly to the adherence of fibrin‐platelet aggregates at the site of the weld.
Laser in situ keratomileusis
Authors: Pallikaris Loannis G. , Papatzanaki Maria E. , Stathi Evdoxia Z. , Frenschock Oliver , Georgiadis Anthimos
Published: March 2007

A new laser refractive procedure is being developed in a rabbit model. With a modified microkeratome, central corneal flaps were created. An ArF excimer laser was used to produce 3‐mm‐diameter circular ablations on the central part of the exposed stromal bed. One group of animals was sacrificed immediately postoperatively, and both the dissected and ablated areas were studied using scanning electron microscopy. A second group of animals was sacrificed 4 weeks postoperatively. In this group, the subsequent healing of the corneas was studied using light microscopy. At 3 days, the wounded stromal areas showed some degree of haze. Haze was progressively reduced over 1 month, but it could be still discerned biomicroscopically. A hemicircular opacification corresponding to the flap edges was also apparent on slit‐lamp examination. Microscopic observation showed that the epithelium was normal, except at the flap margins, where it was thickened. An increased number of keratocytes was observed in the interface between the flap stroma and the ablated area. The procedure might induce stable corneal changes because of the preservation of the anterior layers of the cornea.
Determination of retinal blood velocity with respect to the cardiac cycle using laser‐Triggered release of liposome‐Encapsulated dye
Authors: Khoobehi Bahram , Aly Omar M. , Schuele Kathleen M. , Stradtmann Manrique Ortiz , Peyman Gholam A.
Published: March 2007

A system of selective angiography has been developed for measuring blood velocity in retinal arteries and veins. It uses a lipo‐some‐encapsulated fluorescent dye that is released by application of laser energy in a specific retinal vessel. The method is shown to be able to distinguish between peak systolic velocity and minimum diastolic velocity. In the cynomolgus monkey, the two values were found to differ by approximately a factor of three. It is known that many ocular and systemic diseases affect retinal circulation, and therefore a method of blood velocity measurement with such sensitivity may prove highly valuable in the practice of ophthalmology. As an example, the velocity in a retinal vein was measured before and after partial occlusion by pho‐tocoagulation. The two values obtained were significantly different, and the blood velocity was found to return to the value prior to occlusion when measured at 18 days.
Transscleral application of a semiconductor diode laser
Authors: Peyman Gholam A. , Naguib Khaled S. , Gaasterland Douglas
Published: March 2007

We used a diode laser with an output power of 1 W through a fiberoptic light pipe (200 μm diameter) to deliver laser energy through the sclera of pigmented rabbits. Ciliary body destruction occurred with energy levels of 300–400 mW and exposure time of 0.5 sec. Retinal photocoagulation was achieved with energy levels of 200–500 mW in 0.5 sec. Histologic examination of acute lesions demonstrated thermal destruction of ciliary body processes and retina. Chorioretinal scar formation was observed clinically and histologically within 2–3 weeks. Our data indicate that the transscleral diode laser may be used for destruction of the ciliary body processes or peripheral retinal coagulation in pigmented eyes.
Comparative bactericidai exposures for selected oral bacteria using carbon dioxide laser radiation
Authors: Dederich Douglas N. , Pickard Michael A. , Vaughn Allison S. , Tulip John , Zakariasen Kenneth L.
Published: March 2007

Although relatively high CO2 laser energies have been shown to sterilize root canals, the response of several bacterial strains to decreasing exposures of CO2 laser energy remains unknown. Freshly grown bacterial cells were irradiated on glass microscope coverslips. A comparison of equivalent energy exposures with differing parameters was made on the bacterial viability. No statistically significant difference was found in the energy required to kill closely related bacterial species. However, the energy density required to kill greater than 99.5% of the bacteria is less than 200 J/cm2, much less than that shown to sterilize in a previous study.
Bladder perforation resulting from the use of the neodymium: YAG laser
Authors: Greskovich Frank J. , von Eschenbach Andrew C.
Published: March 2007

Complications resulting from the use of the neodymium:YAG (Nd:YAG) laser to treat superficial bladder cancer are uncommon and are usually associated with abnormally high laser power outputs. We report a case of bladder perforation in a human attributed to the Nd:YAG laser used at a low power setting and comment on those factors that contributed to this complication.
Endoscopic thoracic sympathectomy: Evaluation of pulsatile laser, non‐pulsatile laser, and radiofrequency‐generated thermocoagulation
Authors: Massad Malek , LoCicero Joseph , Matano Jun , Oba Junichi , Greene Rodney , Gilbert Jeremy , Hartz Reneé
Published: March 2007

We describe a modified technique for percutaneous denervation of the thoracic sympathetic chain by laser to treat selected cases of sympathetic causalgia of the upper extremities. The technique involves transpleural ablation with laser under thoracoscopic guidance through the second or third intercostal space‐anterior axillary line. We also compare four different modalities of endoscopic denervation: A xenon chloride excimer laser (308 nm, 35 mJ/pulse, 20 pulses/sec, 2.2 mm catheter tip), CO2, laser (14 W, CW, 2 mm spot size), Nd:YAG laser (88 W, CW, 3 mm spot size), and radiofrequency‐generated thermocoagulation (3 W, CW, 2.1 mm catheter tip) by performing bilateral thoracic sympathectomy on 12 mongrel dogs (three dogs each). Criteria analyzed included duration of exposure, power density, total energy output, laser penetration and spread, gross morphology, and scanning electron microscopy (SEM) of the destroyed neural tissue. Total ablation of the inferior segment of the stellate ganglion and the T1‐T2, nerve roots by excimer laser required 83±1 Joules over an exposure period of 118 seconds. Ablation by CO2, and Nd:YAG laser required 153±13 Joules and 554±47 Joules delivered over 11 and 6 seconds respectively. In contrast, ablation of the same volume of nerve tissue by RF required 810±50 Joules over 270 seconds. SEM evaluation revealed that excimer and CO2, laser lesions were narrower in configuration compared to RF and Nd:YAG lesions which showed more lateral spread. The actual depth of penetration per 1 second exposure was similar for Excimer and CO2, (1.5 mm) and RF (1.3 mm), but deeper for Nd:YAG (3 mm). Our data shows that excimer and CO2, laser produce discrete lesions with minimal damage to surrounding structures. It also demonstrates the safety and reliability of endoscopic denervation, particularly for bilateral denervation which can be performed in one sitting without the added morbidity of a thoracotomy incision.
Gross and microscopic changes in the viscera induced by photodynamic therapy applied to the lower abdomen of intact rats
Authors: Chazen Mark D. , Baggs Raymond B. , Gibson Scott L. , Albert Michael S. , Hilf Russell
Published: March 2007

Photodynamic therapy (PDT) is a promising approach to the treatment of cancer. Preferential retention of the photosensitizer by malignant tissue has been considered a hallmark of this treatment modality. However, photosensitivity can be observed in normal, non‐neoplastic tissues, and the present study investigated the effects of PDT treatment on the abdomen of intact rats. A circular region (1 cm diameter) on the shaved abdomen of Fischer rats, pretreated 24 h prior with Photofrin II, was irradiated for 30 min at 632 nm. Control animals received either photoradiation or Photofrin II administration. Subsequent lesions were observed in the irradiated skin, its associated abdominal wall, and the underlying gut in rats receiving Photofrin II and laser irradiation. All tissues were not equally sensitive to PDT treatment. Gut lesions were consistently more severe than were skin and abdominal wall injuries. By 24 hr after treatment, the gut manifested a transmural hemorrhagic necrosis, while the irradiated skin and abdominal wall were edematous, with an inflammatory infiltrate in the dermis and around occasional swollen myocytes. These results indicate that superficial lesions induced by PDT may not be reliable indicators of the extent of deeper PDT tissue damage. Further, it may be possible to take advantage of this discrepancy in tissue sensitivity and treat deep tissues through less sensitive superficial tissues.
Optical properties of normal, diseased, and laser photocoagulated myocardium at the Nd:YAG wavelength
Authors: Splinter Robert , Svenson Robert H. , Littmann Laszlo , Tuntelder Jan R. , Chuang Chi Hui , Tatsis George P. , Thompson Michelle
Published: March 2007

Laser photocoagulation of the myocardium effectively destroys arrhythmogenic foci. The purpose of this study was 1) to compare the optical properties of canine myocardium before and after photocoagulation, 2) to compare the canine model with clinical cases by measuring the optical properties of human myocardium, and 3) to assess the optical properties of human myocardial scar and epicardial fat tissue. Measured optical properties were the absorption coefficent, μa; scattering coefficient, μs; and scattering anisotropy factor, g. Optical measurements were performed at 1064 nm wavelength on thin plane parallel tissue slices using the integrating sphere method with glass hemispheres on either side of the sample. The study showed 1) an increase of the scattering coefficient by 40% and a two‐ to threefold increase in reduced scattering coefficient as a result of photocoagulation; 2) that the μa (0.035 ± 0.024 mm−1) and μs (17.9 ± 3.8 mm−1) of human myocardium were not significantly different from μa (0.043 ± 0.021 mm−1) and μs (17.3 ± 2.2 mm−1) of canine myocardium, whereas the human g (0.964 ± 0.005) was slightly different from the canine g (0.974 ± 0.008); and 3) that the μa (0.021 ± 0.016 mm−1) of epicardial fat and μs (13.8 ± 1.1 mm−1) of myocardial scar were significantly lower than those of normal myocardium. A dynamic model of laser‐tissue interaction incorporating these changes and inhomogeneities is necessary to better describe light distribution during laser photocoagulation.
Analysis of photoproducts, free radicals, and particulate debris generated during in vivo argon laser myoplasty
Authors: Gal Dov , Fonger James D. , Rastegar Hassan , DeJesus Stephen T. , Clarke Richard H. , Isner Jeffrey M.
Published: March 2007

Catheter‐guided laser myoplasty in a closed ventricle has been advocated for the treatment of hypertrophic cardiomyopathy, ablation of arrythmogenic foci, and transmyocardial laser revascularization of ungraftable regions of ischemic myocardium. The purpose of this study was to evaluate the nature of particulate debris and photoproducts generated in vivo. Accordingly, cardiopulmonary bypass was established in four dogs without active cooling and an apical left ventricular vent was placed. In two dogs, a laser catheter was inserted into the cardioplegia‐arrested left ventricle through the left atrial appendage and across the mitral valve. In the other two dogs the laser catheter was inserted into a perfused, fibrillating left ventricle retrograde across the aortic valve. Myocardial ablation of the ventricular septum was performed using continuous argon‐ion laser irradiation (8–10 watts, 4–11 minutes) and blood samples were drawn through the ventricular vent. The final ablation in each dog was done during a separate ventricular flush with a chemical “spin trap” capable of detecting free radicals. Analysis of ventricular effluent revealed levels of carboxyhemoglobin and hydrogen cyanide which were well below accepted clinical toxic limits. Microparticulate debris (2‐300 femtoliter) was not detected. Evidence of trace free radical generation was suggested in one of four dogs.

In conclusion, closed ventricular argon laser myoplasty did not generate clinically significant levels of the toxic photoproducts we measured, or microparticulate debris. These in vivo findings suggest that the clinical application of catheter‐based laser myoplasty will not be limited by the generation of these toxic photoproducts or microembolic debris.
Co:MgF2 laser ablation of tissue: Effect of wavelength on ablation threshold and thermal damage
Authors: Schomacker Kevin T. , Domankevitz Yacov , Flotte Thomas J. , Deutsch Thomas F.
Published: March 2007

The wavelength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical absorption length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 μm, a wavelength region in which the absorption length varies by a decade. For soft tissues the ablation threshold tracks the optical absorption length; for bone there is little wavelength dependence, consistent with the low water content of bone. Thermal damage vs. wavelength was also studied for cornea and bone. Thermal damage to cornea has a weak wavelength dependence, while that to bone shows little wavelength dependence. Framing‐camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion.
Photodynamic therapy for rat pituitary tumor in vitro and in vivo using pheophorbide‐a and white light
Authors: Yano Takashi , Uozumi Tohru , Kawamoto Keiichi , Mukada Kazutoshi , Onda Jun , Ito Akihiro , Fujimoto Nariaki
Published: March 2007

This is the first report on the use of photodynamic therapy (PDT) for rat pituitary tumor in vivo. Rat pituitary tumor (GH3) cells were cultured, GH3 tumor was subcutaneously implanted in nude mice, and pheophorbide‐a (Ph‐a) and white light were prepared. Photocytotoxicity proportional to Ph‐a concentration, intensity of irradiation, and incubation time was observed in vitro. Despite the delay in the disappearance of Ph‐a from the tumor, Ph‐a in the pituitary gland rapidly decreased after intravenous administration in vivo. Through PDT, the tumor grossly disappeared, the plasma levels of rat growth hormone secreted from the tumor also remarkably decreased, and the development of giantism was inhibited. These results indicate that PDT is effective against rat pituitary tumor.
Interspersion of fragmented fiber's splinters into tissue during pulsed alexandrite laser lithotripsy
Authors: Strunge Christian , Brinkmann Ralf , Flemming Gabriela , Engelhardt Ralf
Published: March 2007

Laser induced shockwave lithotripsy (LISL) on artificially inserted human renal calculi was realized in explanted pig ureters. A pulse stretched Alexandrite solid state laser was used at 750nm. Pulses of 350ns and 1μs duration were transmitted through a 250μm all silica fiber onto a stone surface, keeping the fiber tip in contact with a stone close to the ureter wall. The high power density of the 350ns pulses lead to an optical breakdown inside the distal fiber tip causing fiber fragmentation of about 28mm/100 pulses. Deep penetration of the fiber fragments into the ureter wall was proven histologically. Fiber fragmentation was avoided by increasing the pulse duration up to 1μs. Risks for patient treatment caused by short pulse lithotripsy are discussed.
Rate process parameters of albumen
Authors: Yang Y. , Welch A. J. , Rylander H. G.
Published: March 2007

Both egg white and egg yolk are excellent media for studying photocoagulation due to thermal response of tissue to laser light. They are readily available, consistently the same, and provide a standard biological medium for different labs to compare results. The irradiation parameters for laser coagulation of these media depend upon their optical properties and their temperature‐dependent rate reactions.

Estimates of the rate process damage coefficients were obtained from constant‐temperature water bath experiments. The activation energy E for egg white was estimated to be 92,000 (cal/(M*K)) and the integration constant A was found to be 3.8 × 1057 (second−1).
Fluorescence guided excimer laser ablation of intervertebral discs in vitro
Authors: Buchelts Martin , Katterschafka Thomas , Horvat Rainhard , Kutschera Hans‐Paul , Kickinger Wolfgang , Laufer Günther
Published: March 2007

Laser induced fluorescence of intervertebral discs was investigated in this study for the first time in order to develop a fluorescence guided percutaneous excimer laser discectomy. For this purpose 35 human cadaveric intervetebral discs from level L1 to L5 were irradiated with a 308 nm XeCl excimer laser with a 60 nsec pulse width at 10, 20 and 30 mj/mm2. Laser light was transmitted over a 1000 μm core optical fiber. Fluorescence emitted from the irradiated tissue was transmitted back over the same fiber over a semireflective mirror to another optical fiber, coupled into a spectrograph and O‐SMA optical simultaneous multichannel spectral analyzer system. The spectral lineshape of both the annulus fibrosus and the nucleus pulposus was characterized by a broadband emission between 320 nm and 616 nm with 3 peak emissions at 358, 423 and 457 nm. Relative intensities were calculated by forming two ratios of the peak intensities of the three peaks (R1 = I 423 / I 358; R2 = I 423 / I 457). Statistical analysis of both ratios revealed a highly significant discrimination between annulus fibrosus and nucleus pulposus (P < 0.001). Under penetrating conditions multiple recorded spectra showed the spectral profile of subsequently ablated nucleus and annulus. The results of this study demonstrate that discrimination between annulus fibrosus and nucleus pulposus by excimer laser‐induced fluorescence is feasible under laboratory conditions. Fluorescence spectroscopy could possibly be developed into a valuable guiding system for percutaneous laser discectomy.
Laser resistant stainless steel endotracheal tube: Experimental and clinical evaluation
Authors: Fried Marvin P. , Rao Mallampati S. , Liu Fang‐Cheng , Kaplan Stuart , Caminear David S. , Samonte Bernadette R.
Published: March 2007

A fire due to endotracheal tube (ET) ignition is a catastrophic event that may occur during laser surgery of the upper airway, regardless of the wavelength utilized. Although methods exist that permit laser surgery without an ET, this is frequently not feasible. The current investigation was undertaken to evaluate the efficacy of a double‐cuffed stainless steel ET, first in the laboratory and subsequently in a clinical setting. Bench testing was performed using CO2, (both standard and milliwatt) and KTP/532 lasers. Only the distal polyvinyl chloride cuffed end of the tube was potentially ignitable, however, the appropriate use of saline to fill the cuffs allowed only for cuff perforation without ignition. Canine testing was performed in 10 animals: 4 dogs were intubated from 3 to 4.5 hours with the laser resistant stainless steel endotracheal tube (LRSS‐ET) (Laser‐Flex Tracheal Tube; Mallinckrodt Anesthesia Products, St. Louis, MO) and 2 with an aluminum tape wrapped red rubber ET. Visual and histological examination were performed in both groups at 3 and 7 days. Four dogs underwent CO2, laser laryngeal surgery with visual and histological examination performed at 7 days postoperatively. No untoward effects could be demonstrated due to the LRSS‐ET. A clinical study was then performed in 24 patients who underwent laser surgery of the upper aerodigestive tract with either a CO2 or KTP/532 laser. In all cases ventilation was adequate, the shaft of the LRSS‐ET proved impervious to the laser, and the distal end of the tube protected the tracheobronchial tree safely. It is concluded that the LRSS‐ET is effective and safe in both CO2 and KTP‐532 laser surgery of the upper airway when ET intubation is deemed necessary.
Optical properties of human sclera, and their consequences for transscleral laser applications
Authors: Vogel Alfred , Dlugos Christian , Nuffer Roland , Birngruber Reginald
Published: March 2007

The spectral dependence of the optical properties of human sclera adjacent to the limbus was investigated and related to the potentials of transscleral photocoagulation. The total transmission, absorption, and reflection, as well as the angular distribution of the transmitted and reflected light were measured at five laser wavelengths (442 nm, 514 nm, 633 nm, 804 nm, and 1,064 nm), both for noncontact and contact applications. Absorption and scattering coefficients were determined using the Kubelka‐Munk model for light propagation through a scattering tissue. The scleral transmission is only 6% at 442 nm but increases to 35% at 804 nm and to 53% at 1,064 nm. The absorption is high at short wavelengths with 40% at 442 nm but it is only 6% at 804 nm and 1,064 nm. The reflection is generally higher than 40% and shows little wavelength dependence. The transmitted light is scattered diffusely at short wavelengths, but at 804 nm and 1,064 nm it exhibits a fairly narrow angular distribution in forward direction. Fiber contact leads to an increase of transmission, with a factor of 3.5 at 442 nm, of 2.0 at 804 nm, and 1.5 at 1,064 nm. Our results indicate that the diode laser (804 nm) and the Nd:YAG laser (1,064 nm) with contact delivery are best suited for transscleral photocoagulation.
Laser trabecular ablation (LTA)
Authors: Hill Richard A. , Baerveldt George , Ozler Serdar A. , Pickford Michael , Profeta Glen A. , Berns Michael W.
Published: March 2007

As part of a pilot study for glaucoma surgery, the use of 3 infrared solid state lasers with 4 fiber optic delivery systems to ablate human trabecular meshwork was investigated. Laser trabecular ablation (LTA) was attempted with the Erbium:YAG (2.94 μm), Erbium:YSGG (2.79 μm), and Holmium:YSGG (2.1 μm) lasers. Laser energy was delivered as a single pulse (250 μs) by tissue fiber optic contact with low hydroxyl‐fused silica (200 and 500 μm), zirconium fluoride (250 μm), or sapphire (250 μm) fiber optics. Total energy required and thermal effects decreased as laser wavelength increased. LTA was best achieved at 2.94 μm (4 mJ total energy; energy densities = 8.2–12.7 J/cm2; pulse length 250 μs) with average thermal damage zones of 5.3–10.3 ± 1.3–2.4 μm (means ± SDs) to contiguous structures. This finding has potential applications in the surgical treatment of open‐angle and congenital glaucoma and may minimize failure rates seen in other types of surgery on the trabecular meshwork where disrupted trabecular meshwork is not removed.
Photodynamic therapy in gastrointestinal cancer
Authors: Karanov Strashimir , Shopova Maria , Getov Hristo
Published: March 2007

Six patients with an early stage of gastrointestinal (GI) cancer (T1NoMo, stage I) were successfully treated by photodynamic therapy (PDT) as follows: esophagus‐1, stomach‐2, rectum‐3. The patients were photosensitized 72 hrs prior to treatment with pure hematoporphyrin at a dose of 5.10−6 kg/kg b.w. in a slow intravenous infusion. Argon‐pumped dye laser light at 0.630 μm wave‐length was used in single and multiple treatment sessions with the power density ranging from 0.015 to 0.192 W.m−2 and a dose varying from 0.320 to 1.600 kJ.m−2. Tumor eradication (complete response) was obtained in each of the patients. No early or late treatment related complications were recorded. The patients were followed‐up in the course of 7–16 months after treatment and no local recurrence or general development of disease (metastases) were reported. PDT in the early stage of GI carcinoma was recognized as a radical therapeutic method in clinical oncology.
Direct comparison of in‐vitro and in‐vivo photofrin‐II mediated photosensitization using a pulsed KTP pumped dye laser and a continuous wave argon ion pumped dye laser
Authors: Ferrario Angela , Rucker Natalie , Ryter Stefan W. , Doiron Daniel R. , Gomer Charles J.
Published: March 2007

A pulsed KTP pumped dye laser (25 kHz repetition rate and 470 nsec pulse width) has been compared to a continuous wave argon ion pumped dye laser as the source of 630 nm light during in‐vitro and in‐vivo Photofrin‐II mediated photosensitization studies. Individual experiments documented the effectiveness of each laser system on a) photosensitizer induced cytotoxicity and induction of stress protein synthesis using Chinese hamster fibroblasts; b) photobleaching of Photofrin‐II in aqueous solution; c) Photofrin II mediated photosensitization of normal mouse skin; d) Photofrin II mediated photodynamic therapy of a mouse mammary carcinoma; and e) tumor temperature levels generated during laser exposure. Comparable results were obtained for both laser systems in all experiments.