bluuebunny/crossref_metadata_2025 huggingface dataset:
Crosslinking of extracellular matrix proteins: A preliminary report on a possible mechanism of argon laser welding
Authors: Murray Louann W. , Su Lyndon , Kopchok George E. , White Rodney A.
Published: March 2007

In order to elucidate the biochemical mechanism of laser welding of tissues, we have compared protein profiles from argon laser–treated specimens with controls. Extracellular matrix components from untreated and laser‐welded skin and blood vessels were extracted with guanidine hydrochloride and separated by SDS polyacrylamide gel electrophoresis. When compared with matched, untreated tissues, protein electrophoretic profiles from laser‐treated samples showed several changes. In both tissue types, argon laser treatment decreased the concentration of a 235 kd protein that migrates between the alpha and beta chains of type I collagen. Laser‐treated blood vessels showed significantly more low molecular weight protein at the dye front than in control tissue, whereas significantly more high molecular weight protein appeared in laser‐treated skin samples when compared with untreated tissue. These results suggest that the argon laser may either degrade or crosslink proteins in vivo. Laser‐induced protein crosslinks may be the biochemical basis of argon laser welding.
Possibility of choriocapillary occlusion under experimental subretinal hemorrhage by photocoagulation with lasers of different wavelengths
Authors: Miki Tokuhiko , Inoue Kazunori , Obana Akira , Shiraki Kunihiko
Published: March 2007

To clarify the possibility of occluding choroidal neovascularization in subretinal hemorrhage with various laser wavelengths, lesions of experimental subretinal hemorrhage were photocoagulated with argon, dye, and krypton lasers and were examined by light and electron microscopy. Our experimental results revealed that laser photocoagulation with wavelengths longer than 590 nm was effective in occluding the choriocapillaries under a thin subretinal hemorrhage. Complete occlusion of choriocapillaries was accomplished by red dye laser (630 nm) or krypton red laser. The choroidal lesion coagulated by 590 nm dye laser showed more extensive reaction than the other lesions at a posttreatment interval of 7 days. The red dye laser (630 nm) or krypton red laser is recommended for the treatment of neovascular maculopathy under thin subretinal hemorrhage because of less reaction and complete occlusion of the choroidal neovascularization.
Catastrophic injury secondary to the use of coaxial gas‐cooled fibers and artificial sapphire tips for intrauterine surgery: A report of five cases
Authors: Baggish Michael S. , Daniell James F.
Published: March 2007

Five women undergoing endometrial ablation with the Nd‐YAG laser developed sudden gas embolism. In each case laser intrauterine contact surgery was carried out utilizing coaxial fibers with (three cases) and without (two cases) artificial sapphire tips but commonly cooled by air or nitrogen. Four of the five women died in a sequence of sudden cardiovascular collapse followed by irreversible cardiac arrest. One woman was critically ill and following prolonged hospitalization survived with neurological deficits.
Helium‐neon laser‐induced respiratory burst of phagocytic cells
Authors: Karu T. I. , Ryabykh T. P. , Fedoseyeva G. E. , Puchkova N. I.
Published: March 2007

The effect of He‐Ne laser radiation (λ = 632.8 nm, I = 6.8 W/m2, irradiation time from 5 to 50 sec) on kinetics of spontaneous and Candida ablicans‐stimulated chemiluminescence of mouse spleen cells was studied. It was found that laser radiation caused significant enhancement (180–250%) both of spontaneous chemiluminescence and Candida‐induced chemiluminescence. The effective dose interval ranges from 100 to 300 J/m2, with a maximum at 200 J/m2. This finding shows that He‐Ne laser irradiation can induce the respiratory burst (generation of reactive oxygen species having bactericidal activity) of phagocytic cells.
Effect of Nd:YAG laser energy on articular cartilage healing in the dog
Authors: Hardie Elizabeth M. , Carlson Cathy S. , Richardson Daniel C.
Published: March 2007

The effect of low dose neodymium:yttrium aluminum garnet (Nd:YAG) laser therapy on cartilage healing was studied. Partial‐ and full‐thickness cartilage defects were surgically created in the femoral condyles of 20 adult dogs. The cartilage defects in one limb of each dog were exposed to 30 J of Nd:YAG laser energy. The dogs were euthanatized 1 week (n = 6), 1 month (n = 7), and 6 months (n = 7) after surgery. Plastic‐embedded, undecalcified histologic sections of each cartilage defect were examined for evidence of cartilage healing. Special stains were used to determine the type of repair tissue present, and morphometric measurements of repair tissue were made. No effect of Nd:YAG laser therapy on cartilage healing was noted.
Irradiation of pigmented melanoma cells with high intensity pulsed radiation generates acoustic waves and kills cells
Authors: Ara Gulshan , Anderson Rox R. , Mandel Krishna G. , Ottesen Michel , Oseroff Allan R.
Published: March 2007

Photokilling of pigmented mouse melanoma cells (B‐16) was investigated using pulsed high intensity visible radiation. Melanin acts as an endogenous chromophore, and 694 nm radiation with 40 nsec pulse duration and 0.53 × 107w/cm2 intensity causes cell death. Irradiation of non‐pigmented human melanoma cells (Ul) or human squamous carcinoma cells (FaDu) under similar conditions did not kill the cells. Also, irradiation of B‐16 cells with 300 μsec laser pulses (103W/cm2) or with continuous wave (CW) radiation (10p−3 W/cm2) did not kill the cells. These data indicate that pigmented cell killing is due to absorption of radiation by melanin and that the pulsewidth and intensity of radiation play important roles in cell killing. The generation of acoustic waves due to absorption of the pulsed radiation by pigmented cells and by isolated melanosomes was demonstrated at 532 and 625 nm and 8.5 nsec pulse duration (107–108 W/cm2); the amplitudes of the acoustic signals were approximately 2.5‐3.0‐fold higher at 532 nm compared with 625 nm, and they increased with increasing fluence. In contrast, irradiation of U1 or FaDu cells with comparable fluences and intensities did not generate acoustic waves. A possible correlation between the generation of photoacoustic waves and pigment cell death is proposed. Since the thermal relaxation time of melanosomes is 0.5–1.0 μsec, the mechanism proposed is that thermal confinement of high intensity, short‐pulse visible radiation generates acoustic waves by thermal expansion, leading to mechanical damage to the cells.
Assessment of laser‐Induced release of drugs from liposomes: An in vitro study
Authors: Khoobehi Bahram , Char Clifford A. , Peyman Gholam A.
Published: March 2007

We evaluated the characteristics of laser‐induced release of an antimetabolite (cytosine arabinoside) from temperature‐sensitive liposomes. Previous work had shown that a laser would induce breakdown of liposomes when a dye was encapsulated within the liposomes. The present investigation was performed to determine if release could be induced from liposomes that did not contain dye. In vitro, dynamic studies of the release of the drug from liposomes diluted in blood (flowing in a capillary tube at 40 μm/min) were conducted using an argon dye laser operating either in the blue‐green mode (488/514 nm) or in the dye mode (577 nm). A radio‐labeled marker was used to monitor the drug release. The results showed that the drug could indeed be released from liposomes that did not contain dye, at energy levels that are not likely to be harmful to the tissue. At identical power levels, the release of the drug was greater at 577 nm than at 488/514 nm, probably owing to the greater light absorbance of hemoglobin at the longer wavelength. The results indicate the potential for the site–specific release of a variety of molecules in the ocular vasculature.
Thermal damage produced by high‐lrradiance continuous wave CO2 laser cutting of tissue
Authors: Schomacker Kevin T. , Walsh Joseph T. , Flotte Thomas J. , Deutsch Thomas F.
Published: March 2007

Thermal damage produced by continuous wave (cw) CO2 laser ablation of tissue in vitro was measured for irradiances ranging from 360 W/cm2 to 740 kW/cm2 in order to investigate the extent to which ablative cooling can limit tissue damage. Damage zones thinner than 100 μm were readily produced using single pulses to cut guinea pig skin as well as bovine cornea, aorta, and myocardium. Multiple pulses can lead to increased damage. However, a systematic decrease in damage with irradiance, predicted theoretically by an evaporation model of ablation, was not observed. The damage‐zone thickness was approximately constant around the periphery of the cut, consistent with the existence of a liquid layer which stores heat and leads to tissue damage, and with a model of damage and ablation recently proposed by Zweig et al.
Laser balloon angioplasty: Technical realization and vascular tissue effects of a modified concept
Authors: Ischinger Thomas , Coppenrath Klaus , Weber Helmut , Enders Susanne , Ruprecht Lutz , Unsöld Eberhard , Hessel Stefan
Published: March 2007

A modified concept using a movable fiber with radial light dispersion was developed for combining mechanical balloon dilatation and intraluminal circumferential Nd‐Yag laser irradiation of the arterial wall. The aims of the study were the technical feasibility and the acute and chronic vascular tissue effects of laser‐assisted balloon dilatation. The carotid arteries (n = 9 dogs) and femoral arteries (n = 5 dogs) of dogs were mechanically dilated and simultaneously circumferentially irradiated through the balloon by 1,064 nm Nd‐Yag laser (20‐25 W). Temperature at the adventitial surface was kept constant at 50°C, 60°C, 70°C, or 80°C for either 8 or 15 seconds by a computerized feedback system for temperature control. Angiographic and histological results were available acutely, subacutely (2 days), and at 3 months. Angio‐graphically, stable and smooth enlargement of the lumen was demonstrated acutely. At 3 months, occlusions, probably throm‐botic in origin, had occurred in 5 of the carotid arteries and none of the femoral arteries. Histologically, laser‐induced coagulation of the arterial wall with loss of cellular elements was demonstrated. Collagen and elastic fibers remained relatively intact. In two carotid arteries intimal proliferation was observed at the treated site. Thus, this technique appears to be technically feasible, yet further study is needed to assess its potential to reduce or repair acute vascular complications (dissections) and to reduce restenoses after percutaneous transluminal coronary angioplasty (PTCA). However, the clinical value of this technique appears to be limited in view of the thromboses and reactive proliferations observed in this preliminary study.
Combination studies of hyperthermia induced by the neodymium: Yttrium‐Aluminum‐Garnet (Nd:YAG) laser as an adjuvant to photodynamic therapy
Authors: Mang Thomas S.
Published: March 2007

Photodynamic therapy (PDT) and hyperthermia have been investigated as treatments for several types of tumors. Studies have been done to determine the efficacy of each modality individually and recently in combination with each other. In this study, 630‐nm light was delivered by an argon‐dye laser and hyperthermia was induced using an Nd:YAG laser. Both lasers offer the ability of delivering the beams through a quartz fiberoptic alone or simultaneously. This study examines the efficacy of the simultaneous administration of PDT and selective hyperthermia at 44.5°C in tumor control in the spontaneous mammary tumor (SMT‐F) in DBA mice. Hyperthermia alone (44,5°C, 30 min) resulted in complete destruction of tumors, with no subsequent regrowth in 6.6% of the mice treated. PDT alone (5 mg/kg dihe‐matoporphyrin ether; 135 J/cm) resulted in a cure rate of approximately 10%, and the simultaneous treatment of the modalities resulted in a 32.8% cure rate after 90 days. These values are indicative of a synergistic interaction.
Continuous laser radiation effect at 1.06 μm on gastrointestinal tract
Authors: Korolyov Victor A. , Grigoryants Vil V.
Published: March 2007

The thermal effect of 1.06 μm YAG:Nd laser irradiation at temperature conditions up to 100°C without crater formation on gastrointestinal (GI) tissue samples was investigated. The theoretical and experimental data show that at an intensity of 160‐400 W/cm2 laser‐induced heating of the tissue with an initial temperature of 20°C leads to coagulation lesions at a temperature no less than 60°C and at a depth of 1.7–2.1 mm.
Nd:YAG coagulation of the verumontanum: An endoscopic attempt at sterilization
Authors: Gilbert Peter T. O. , Kramer Elke , Beckert Rainer , Treiber Uwe
Published: March 2007

In order to develop a new and less invasive method of sterilization in men we performed photocoagulation of the verumontanum in 10 rams, using a Nd:YAG laser, wavelength 1,060 nm. Under general anesthesia a perineal urethro‐cutaneous fistula was achieved, and, by means of a 16F laser‐endoscope, transure‐thral coagulation of the ejaculatory ducts, located in the verumontanum, was carried out, using pulses of 1.5 sec in duration and 20‐30 W in power. The animals were killed at different postoperative time intervals, ranging from 1 day to 8 weeks. Injection of methylene‐blue into the testicular ducts of the resected prostate‐bladder specimen and histologic studies of the coagulated tissue revealed that complete bilateral occlusion of the ejaculatory ducts had been achieved in 4 rams. Failures were due to over‐extended irradiation of the verumontanum.

Except for urinary tract infections occurring in 4 animals, no serious complications were encountered.

Further investigations are still necessary to determine the role of lasers in male sterilization.
Cell selectivity to laser‐induced photoacoustic injury of skin
Authors: Yashima Yutaka , McAuliffe Daniel J. , Flotte Thomas J.
Published: March 2007

Cell selectivity to photoacoustic injury induced by argon‐fluoride excimer laser (193 nm) was studied. Rats were irradiated through air or water and a 2.5 mm aperture. The laser was adjusted to deliver 150 mJ/cm2 at the skin surface with 12 and 24 pulses. Immediate damage was assessed by transmission electron microscopy. Cell selectivity was observed in dermis and epidermis. Fibroblasts showed alteration of nuclear chromatin and cytoplasmic organelles, while some of the migratory cells adjacent to fibroblasts did not. Similar difference of damage was observed between keratinocytes and Langerhans cells in epidermis. Considering the relationship between cells and their microenvironment in tissue, this selectivity may be due to the difference of acoustical coupling of propagation of acoustic waves rather than to differential sensitivity of the cells to damage.
Fragmentation of biliary stones with a 308 nm excimer laser
Authors: Shi Weiqiang , Papaioannou Thanassis , Daykhovsky Leon , Vari Sandor G. , Grundfest Warren S.
Published: March 2007

The use of a XeCl excimer laser (308 nm) for biliary stone frag mentation is reported. Laser energy is delivered via UV grade fused silica fibers to the target stones immersed in normal saline solution. Sixty biliary calculi—pigment (n=40), and cholesterol (n=20)—were fragmented in vitro. The total energy delivered per unit mass of the stone is kept constant. Two energy fluences (80 and 110 mJ/mm2) at two repetition rates (5 and 20 Hz) delivered through fibers of two core sizes (300 and 600 μm) are utilized to study the effect of different laser parameters on the fragmentation process. Although both pigment and cholesterol stones are susceptible to excimer laser fragmentation, higher fragmentation efficiency is obtained for the pigment stones than for the cholesterol stones. Our study suggests that higher energy fluence and larger fiber core size result in higher fragmentation efficiency for pigment stones. Fragmentation thresholds at stone surface for a variety of biliary calculi of known composition were measured. The threshold energy fluence is approximately 3 mJ/mm2 and 17 mJ/mm2 for pigment and cholesterol stones, respectively. Our study indicates that the 308 nm excimer laser may be effective as a laser lithotriptor with low threshold and good efficiency for biliary stone fragmentation.
Modeling of tissue heating with a pulsed Nd:YAG laser
Authors: Grossweiner Leonard I. , Al‐Karmi Anan M. , Johnson Porter W. , Brader Kevin R.
Published: March 2007

Temperature profiles were measured in large sections of bovine muscle and bovine liver exposed to single pulses from a clinical Nd:YAG laser. The data were analyzed with a photothermal model applicable to an incident gaussian beam including the effects of beam spread and heat flow. Closed form expressions for the radial average initial temperatures and thermal relaxation were derived and compared with the measurements.
Carbon dioxide milliwatt laser in the vasovasostomy of vas deferens in dogs: Part I
Authors: Krisch Evan B. , Seidmon E. James , Samaha A. Michael , Phillips Steven J. , Tang Chik‐Kwun , Shea Francis J.
Published: March 2007

This is the first arm of a two prong study conducted to learn two different aspects of vasovasostomy in dog vas deferens using the milliwatt carbon dioxide laser. The first study involved the evaluation of patency without collection of sperm.

Six dogs were evaluated and all underwent vasectomy and subsequently had vasovasostomies performed between 4 and 12 weeks utilizing two approximating sutures and welding with the milliwatt carbon dioxide laser. Metal clips were used for both X‐ray analysis and localization of the vasovasostomy site.

In this investigation a vasogram was performed. Dogs were sacrificed at 4, 6, and 8 weeks postvasovasostomy. The vasovasostomy specimens were studied with electron microscopy and histological evaluation. The vasovasostomy was completed in under 120 minutes using this laser‐assisted technique and was found to be a viable and promising technique for vasovasostomy.
Characterization of the site dependency of normal canine arterial fluorescence
Authors: Garrand Timothy J. , Stetz Mark L. , O'Brien Kenneth M. , Gindi Gene R. , Laifer Lawrence I. , Deckelbaum Lawrence I.
Published: March 2007

The difference in fluorescence between normal and atherosclerotic artery has been proposed as a feedback mechanism to guide selective laser ablation of atherosclerotic plaque. This fluorescence difference is due to the relative difference in collagen:elas‐tin content of normal artery and atherosclerotic plaque. However, normal arteries have site‐dependent variation in collagen: elastin content which may affect their fluorescence spectra. To evaluate the site dependency of normal arterial fluorescence, helium‐cadmium (325 nm) laser‐induced fluorescence spectra were analyzed in vitro from the ascending aorta, abdominal aorta, and carotid, femoral, renal, and coronary arteries (N=57) of 12 normal mongrel dogs. Elastin and collagen contents were determined for a subset of these arteries (N=15). The spectral width of normal arterial Fluorescence varied by site and correlated with the measured collagen:elastin content at each site (r=‐0.84, P < 0.005). Fluorescence spectra were decomposed into collagen and elastin spectral components by using a linear model with a least‐squared error criterion fit. The derived collagen and elastin spectral coefficients correlated with the measured collagen and elastin tissue content (r=0.75 and 0.83 respectively, P < 0.005). Thus, the fluorescence spectra of normal arteries is site dependent and correlates with the collagen:elastin content. Therefore, spectral feedback algorithms for laser angioplasty guidance must be site specific.
Carbon dioxide laser oral safety parameters for teeth
Authors: Powell G. Lynn , Whisenant Brian K. , Morton Thomas H.
Published: March 2007

The carbon dioxide laser is used in the oral cavity for a variety of procedures. Although the procedures may not involve the teeth directly, precaution should be exercised to preserve their integrity. The results of this study indicate that the most limiting parameter for oral use of the CO2 laser is damage to the enamel surface, which could be inflicted with as little as 5 W for 0.2 second and a 1 mm beam. Care should be exercised to prevent inadvertent damage to the surface enamel of teeth even at very low energy levels.
Holmium:YAG laser ablation of vascular tissue
Authors: Kopchok George E. , White Rodney A. , Tabbara Marwan , Saadatmanesh Vahid , Peng Shi‐Kaung
Published: March 2007

The ablation of atherosclerotic lesions without collateral thermal or shock wave damage is thought to be a key element for successful laser angioplasty. This study evaluated the effectiveness of pulsed holmium:YAG laser (2.1 μm wavelength) for this application. Fresh normal tissue (n = 139) and arteriosclerotic canine arteries (n = 21) as well as formalin‐preserved normal canine (n = 31) and atherosclerotic human arteries (n = 177) were irradiated under saline via a 600 μm diameter fiber placed perpendicular to the intimal surface with 0–10 gm of force. The laser was operated in the free running mode (FRM; 250 μsec pulsewidth, 5 Hz, 30–7,100 mJ/mm2) and in the Q‐switched mode (QSM; 200 nsec pulsewidth, 6 Hz, 30–1,100 mJ/mm2). Following the experiments, the samples were prepared for histologic and morphomet‐ric analysis. Ablation thresholds in the FRM were 60 and 180 mJ/mm2 in fresh and preserved canine tissue, respectively. Ablation thresholds in the QSM for fresh and preserved canine tissues were 75 and 180 mJ/mm2, respectively. Thresholds for human atherosclerotic tissue were dependent on the amount of calcification. In the QSM and FRM, there were no samples that could not be penetrated at 1,100 mJ/mm2 and above. Histologic examination of the FRM samples revealed confined columns of tissue ablation, with approximately 55–250 μm and 70–140 μm zones of thermal effect being apparent in the fresh and formalin‐preserved samples, respectively. The QSM samples (fresh and preserved) revealed minimal thermal effect (0–20 μm) to the in‐tima and media (smooth muscle cells) between 300 and 1,100 mJ/ mm2, whereas thermal effect in the adventitia (collagen) was 64–172 pm with the same energy fluence. We conclude (1) that the thermal effect can be optimized by shortening the pulsewidth (Q switching at 200 nsec) or by limiting the total energy delivered and (2) that controlled ablation of both normal and atherosclerotic vascular tissue can be accomplished with the holmium:YAG laser.
Lasers for otosclerosis—which one if any and why
Authors: Lesinski S. George
Published: March 2007

Laboratory stapedotomy and stapedectomy revisions were performed in human temporal bones while pyroelectric wave energy analyzers and ultrasensitive thermocouples measured energy absorption at the stapes footplate and in the vestibule. Analysis of these data shows that the visible lasers (argon and KTP‐532) possess ideal optical properties and precision for otosclerosis surgery but conversely have less than ideal tissue characteristics. The CO2laser possesses ideal tissue characteristics. Recent advances in optical engineering and pulsing the energy have increased the precision of this laser to now provide the accuracy required for delicate microsurgery.

Two clinical studies analyze the long‐term hearing results and complications in patients who had undergone CO2laser stapedectomy revision (59 patients) and CO2laser stapedotomy (153 patients). The advantages that these laser techniques provide over conventional surgery methods are discussed.
Pulsed carbon dioxide laser ablation of burned skin: In vitro and in vivo analysis
Authors: Green Howard A. , Domankevitz Yacov , Nishioka Norman S.
Published: March 2007

Pulsed lasers produce efficient and precise tissue ablation with limited residual thermal damage. In this study, the efficiency of pulsed CO2 laser ablation of burned and normal swine skin was studied in vitro with a mass loss technique. The heats of ablation for normal and burned skin were 2,706 and 2,416 J/cm3 of tissue ablated, respectively. The mean threshold radiant exposures for ablating normal skin and eschar were 2.6 J/cm2 and 3.0 J/cm2, respectively. Radiant exposures greater than 19 J/cm2 produced a plasma, which decreased the efficiency of laser ablation. Thus the radiant exposures for efficient ablation range from 4 to 19 J/cm2, and within this radiant exposure range 20–40 μm of tissue are ablated per pulse. We also examined, on a gross and histo‐pathologic basis, in vivo burn eschar excision with a pulsed CO2 laser. The laser allowed bloodless excisions of full thickness burns on the backs of male hairless rats. The zone of thermal damage was approximately 85 μm over the subjacent fascia. The pulsed CO2 laser can ablate burn eschar efficiently, precisely, and bloodlessly and may prove valuable for the excision of burned and necrotic tissue.
Limitations of a thermal camera in measuring surface temperature of laser‐irradiated tissues
Authors: Torres Jorge H. , Springer Thomas A. , Welch Ashley J. , Pearce John A.
Published: March 2007

Thermal cameras are used in research laboratories to measure tissue temperature during laser irradiation. This study was an evaluation of the accuracy of a 3–5 μm thermal camera and two 8–12 μm cameras in detecting the maximum temperatures of small targets. The size of the targets was within the range of laser spot diameters which are used for vessel welding, angioplasty, and dermatology. The response to a sharp thermal edge was measured and analyzed for the three cameras, which had a scanning rate of 30 frames per second. The response of the 3–5 μm camera to reference black body targets of different sizes was also studied.

It was found that the detector system required an average of 2.44 μs to reach 90% of maximum step response for the 8–12 μm system and 5.85 μs for the 3–5 μm system. With a 3×5 telescope and a 9.5 inch focal distance close‐up lens, the 3–5 μm camera underestimated the temperature of targets smaller than 2.0 mm because of its slow detector response. Although the 8–12 μm camera provides more accurate measurements due to its faster detector response, it still underestimates the temperature of targets smaller than 900 μm, when similar magnification and focal distance are used.

Methods to compensate for the inaccuracies are discussed, including empirical correction factors and the inverse filtering technique.
Histologic comparison of the pulsed dye laser and copper vapor laser effects on pig skin
Authors: Tan O. T. , Stafford T. J. , Murray S. , Kurban A. K.
Published: March 2007

Albino pig skin was exposed to the copper vapor (CVL) and flashlamp pulsed dye (PDL) lasers at 578 nm with a 3 mm diameter spotsize over a range of fluences until purpura and whitening were first established. The total irradiation time was the parameter that was varied in order for the CVL to reach the desired fluence. The lowest fluence producing each clinical endpoint was designated the threshold fluence: 34 J/cm2 was required to produce purpura using the CVL compared to 7.5 J/cm2 with the PDL laser. Histologically, skin exposed to purpura fluences from the CVL revealed the presence of constricted, disrupted papillary dermal blood vessels with trapped RBC's within them which were unlike those exposed to PDL where the irradiated vessels were dilated and packed with masses of intravascular agglutinated RBC's.

The whitening threshold fluences for the CVL and PDL lasers were 67 J/cm2 and 29 J/cm2, respectively. Streaming of epidermal cells and dermal collagen denaturation were observed in CVL irradiated skin, compared to occasional dyskeratotic epidermal cells and focal dermal collagen denaturation following PDL exposure.

The mechanisms responsible for the clinical and histologic changes produced by the two laser systems are discussed.
Molecular surgery of the basement membrane by the argon laser
Authors: Helmsworth Thomas F. , Wright Creighton B. , Schemer Scott M. , Schlemm Donna J. , Keller Stephen J.
Published: March 2007

Although the argon laser is used successfully to weld a number of different tissues, the underlying chemical and cellular mechanisms for this process are not precisely defined. Consequently, a biochemical model has been developed in vitro using the welldefined extracellular matrix from the murine Engelbreth‐Holm‐Swarm (EHS) sarcoma. Control and experimental samples of EHS basement membranes were irradiated with a Trimedyne argon laser at 500–3,000 Joules/cm2 at 0°C. The samples were diluted into cold phosphate‐buffered saline and allowed to gel at 35°C. The time course of the gelation reaction was followed in a spectrophotometer at 360 nm. Irradiation reduced the absorbance 7.5–15% compared to controls and was independent of the dilution over a 10‐fold range. Gelation was also measured by determining the amount of protein by the Bradford assay that could be collected by centrifugation at 10,000g for 10 minutes. Argonirradiated samples had 30–40% less protein in the precipitate than the controls. The addition of 5 mM beta‐mercaptoethanol to the EHS extract blocked the effect of the laser on the gelation reaction. In addition, when gelation was carried out in the absence of calcium and magnesium, there were no differences between laser‐treated samples and controls. The basement membrane proteins were separated by electrophoresis through polyacrylamide gels under denaturing plus reducing or denaturing and non‐reducing conditions. No differences in the polypeptide composition were noted between irradiated and control samples using either Coomassie‐ or silver‐staining techniques. The irradiated and control samples were also analyzed on 1.5% agarose gels in 10 mm Tris‐HCl, pH 8 containing 0.1% SDS. Both samples produced a single Coomassie‐positive band, but the control migrated at 0.5 and the irradiated sample at 0.6. In sum, the conformation of extracellular matrix proteins can be altered by the argon laser at welding energies at low temperatures, even though no new covalent interactions were observed.
Endometrial ablation for the treatment of menorrhagia: A comparison of patients with normal, enlarged, and fibroid uteri
Authors: Lomano Jack
Published: March 2007

One hundred sixty‐one patients underwent endometrial ablation with the Nd:YAG laser for the treatment of refractory menorrhagia. Patients were divided into one of three groups: those with a normal‐sized uterus; those with an enlarged uterus (> than 10 cm); and those with uterine fibroids, which had been documented clinically, ultrasonographically, or by a combination of hysteroscopy and laparoscopy or by one or the other. All patients were considered candidates for hysterectomy. Both preoperatively and postoperatively, patients monitored their menstrual cycles and evaluated their flow according to predetermined categories of amenorrhea, light flow, normal flow, heavy flow, and severe flow. After treatment, 68% of patients with normal‐sized uterus and 91% of patients with an enlarged uterus (> than 10 cm) and 88%of patients with uterine fibroids became amenorrheic or had light flow. None of the patients in this last group have had to undergo hysterectomy. This study indicates that the patient with an enlarged or fibroid uterus may not have contraindications for endometrial ablation. Endometrial ablation may be effective in at least temporarily controlling bleeding in those patients with enlarged or myomatous uterus.
Influence of probe motion on laser probe temperature in circulating blood
Authors: Hehrlein Christoph , Splinter Robert , Littmann Laszlo , Tuntelder Jan R. , Tatsis George P. , Svenson Robert H.
Published: March 2007

The purpose of this study was to evaluate the effect of probe motion on laser probe temperature in various blood flow conditions. Laser probe temperatures were measured in an in vitro blood circulation model consisting of 3.2 mm‐diameter plastic tubes. A 2.0 mm‐diameter metal probe attached to a 300 μm optical quartz fiber was coupled to an argon laser. Continuous wave 4 watts and 8 watts of laser power were delivered to the fiber tip corresponding to a 6.7 ± 0.5 and 13.2 ± 0.7 watts power setting at the laser generator. The laser probe was either moved with constant velocity or kept stationary. A thermocouple inserted in the lateral portion of the probe was used to record probe temperatures. Probe temperature changes were found with the variation of laser power, probe velocity, blood flow, and duration of laser exposure. Probe motion significantly reduced probe temperatures. After 10 seconds of 4 watts laser power the probe temperature in stagnant blood decreased from 303 ± 18°C to 113 ± 17°C (63%) by moving the probe with a velocity of 5 cm/sec. Blood flow rates of 170 ml/min further decreased the probe temperature from 113 ± 17°C to 50 ± 8°C (56%). At 8 watts of laser power a probe temperature reduction from 591 ± 25°C to 534 ± 36°C (10%) due to 5 cm/sec probe velocity was noted. Probe temperatures were reduced to 130 ± 30°C (78%) under the combined influence of 5 cm/sec probe velocity and 170 ml/min blood flow. In conclusion, laser‐heated metal probe temperatures are reduced by probe motion in blood independent of temperature losses due to blood flow. Probe motion in combination with blood flow markedly decreases probe temperatures.
193 nm excimer laser ablation of bone
Authors: Lustmann Joshua , Ulmansky Mario , Fuxbrunner Amihay , Lewis Aaron
Published: March 2007

The argon fluoride excimer laser is investigated as a cutting‐ablating tool for bone surgery. Quantitative measurements are presented for various fluences of laser energy and number of pulses. Histological data are presented that demonstrate the minimal damage to the surrounding material from the laser interaction. Comparisons are made for non‐decalcified and decalcified bone. The differences observed, as a function of decalcification in the fluences required for specified depth penetration, are noted and a possible explanation is suggested.
Design and evaluation of a fiberoptic fluorescence guided laser recanalization system
Authors: Garrand Timothy J. , Stetz Mark L. , O'Brien Kenneth M. , Gindi Gene R. , Sumpio Bauer E. , Deckelbaum Lawrence I.
Published: March 2007

Current angioplasty techniques for recanalization of totally occluded arteries are limited by the inability to cross the occlusion and by the risk of perforation. A fiberoptic fluorescence guided laser recanalization system was developed and evaluated in vitro for recanalization of 17 human femoral or tibial totally occluded arterial segments (length 1.9–6.8 cm, diameter 2.5–6.0 mm). A 400 or 600 μm silica fiber was coupled to a helium‐cadmium laser (λ = 325 nm) for fluorescence excitation and to a holmium: YAG laser (λ = 2.1 μm) for tissue ablation. Fluorescence was recorded during recanalization after every other holmium laser pulse. During recanalization, each arterial segment was bent 30–90 degrees with respect to the fiber to simulate arterial tortuosity. Ablation continued with fiber advancement as long as the fluorescence confirmed that the target tissue was atherosclerotic. Arterial spectra were classified as normal or atherosclerotic by an on‐line computerized fluorescence classification algorithm (sensitivity 93%, specificity 95%). Normal fluorescence necessitated redirection of the fiber > 30 times per segment to continue recanalization. Fifteen of 17 totally occluded arteries had multiple recanalization channels created following total energy delivery of 40–1,016 Joules per segment with no angiographic or histologic evidence of laser perforation. Two heavily calcified arterial occlusions were not recanalized due to inhibition of holmium: YAG laser ablation by the recording of normal fluorescence spectra. Therefore, this fluorescence guided laser recanalization system appears safe and effective for recanalization of totally occluded arteries and merits in vivo evaluation. However, the lower sensitivity of fluorescence detection of heavily calcified plaques may limit the efficacy (but not safety) of fluorescence guided recanalization of heavily calcified occlusions.
A new concept for a realtime feedback system in angioplasty with a flashlamp pumped dye laser
Authors: Scheu Manfred , Kagel Henning , Zwaan Martin , Lebeau Annette , Engelhardt Ralf
Published: March 2007

The feasibility of using a pulsed dye laser in angioplasty for detection and disintegration of calcified plaques was studied in vitro. A flashlamp—pumped dye laser (495 nm, 2 μs) was used as the exciting source for laser‐induced‐fluorescence (LIF) signals. Spectral data in the 520 nm to 800 nm region of normal intima, calcified plaque and fibro‐fatty plaques were analyzed with an optical multichannel analyzer, using the same fiber for energy delivery and fluorescence diagnostic. Good signal to noise ratio and different spectra for different specimens were obtained within only 2 μs. The spectral difference is caused by selective reabsorption of oxyhemoglobin in the vessel wall. Time resolved LIF‐spectroscopy shows that the fluorescence intensity reaches its maximum value before the maximum laser intensity is delivered. Fluorescence analysis can be performed in less than 300 ns and therefore the laser can be controlled before plasma threshold is reached. The described in vito results can lead to a clinical useful feedbacksystem for energy control of μs lasers in angioplasty if the blood interference effects can be minimized by changing the laser excitation wavelength or staining the tissue.
Argon laser‐assisted anastomoses in medium‐size vessels: One‐year follow‐up
Authors: Kuroyanagi Yutaka , Taguchi Masakatsu , Yano Takashi , Jones Darrell N. , Shionoya Shigehiko
Published: March 2007

Laser‐assisted anastomosis of medium‐size vessels can be performed with satisfactory short‐term patency. This study was undertaken to evaluate patency and structural integrity up to 1 year. An argon laser was used to make bilateral femoral arteriovenous anastomoses in 12 dogs compared to conventional suture method in another 8 dogs. These anastomoses were evaluated for patency and aneurysm formation at 1 hour; 1, 2, 4, and 8 weeks; and 12 months after surgery. All anastomotic sites were patent and without aneurysmal change or luminal narrowing at all harvesting intervals. Histologic examination revealed that within 1 month laser anastomotic sites were almost completely healed and without intimal hyperplasia. In suture anastomoses, foreign‐body reaction remained evident up to 1 year.

Use of the argon laser for medium size vessel anastomoses resulted in excellent patency without aneurysm formation or intimal hyperplasia even in the long term. These data suggest promising clinical applications.
Argon laser initiated resin photopolymerization for the filling of root canals in human teeth
Authors: Potts Thomas V. , Petrou Athos
Published: March 2007

This work was undertaken to determine if 488 nm light is transmitted through dentin in quantities adequate to polmerize resin located several millimeters from the light source (an optical fiber). The spread of polymerization in a camphorquinone activated resin due to 488 nm light emanating from an opaque plastic canal was compared with light emanating from a canal of the same diameter in tooth dentin. Results indicated that irradiation of a resin‐filled chamber via an opaque canal generated a series of ellipsoidal forms, while irradiation via a root canal generated bullet‐shaped forms of much larger volume and weight. The base of these bullet‐shaped forms was flat against the dentin‐resin interface and surrounded the canal. These results indicated that 488 nm argon laser light was transmitted through dentin and could act to polymerize resin at a distance of several millimeters from the canal. Further experiments verified that resin in lateral canals of tooth roots was readily polymerized by 488 nm light applied at low power levels (50 mW). These experiments demonstrate the effectiveness of the argon laser in polymerizing light activated dental resins located within or adjacent to tooth dentin at distances up to several milimeters from the fiberoptic terminus. The flexibility and control that these procedures make possible in the obturation of root canals may lead to substantial improvements in endodontic therapy.
Micron‐resolution ranging of cornea anterior chamber by optical reflectometry
Authors: Huang David , Wang Jyhpyng , Lin Charles P. , Puliafito Carmen A. , Fujimoto James G.
Published: March 2007

Noncontact, high resolution measurements of anterior eye structures using optical coherence domain reflectometry are described. Distances between intraocular structures are measured by directing a beam of short coherence length light onto the eye and performing an interferometric measurement on the optical group delay of reflected signals. Measurements of corneal thickness, corneal excision depth, and anterior chamber depth are demonstrated in vitro, and the location of tissue boundaries is resolved to within ± 2 μm. The full‐width‐half‐maximum longitudinal resolution is 10 μm. Sensitivities to reflected signals as small as 10−10 of the incident power are achieved by heterodyne detection.
Plasma‐mediated ablation of corneal tissue at 1053 nm using a Nd:YLF oscillator/regenerative amplifier laser
Authors: Niemz Mark H. , Klancnik Edward G. , Bille Josef F.
Published: March 2007

Plasma‐mediated ablations were performed on human donor corneas with a short pulsed Nd:YLF laser system at 1053 nm. The pulses were 60 psec in duration at a repetition rate of 1.0 kHz. The laser beam was oriented perpendicular to the cornea surface. The threshold energy densities for ablation of epithelium, Bowman's membrane and stroma were measured. They were 6.1±1.8 J/cm2, 21.0±5.1 J/cm2 and 10.4±1.8 J/cm2, respectively. The mean rate of tissue removal at the stromal energy density threshold was about 1 μm per pulse. The walls of the laser excisions were smooth with distortions of less than 1 μm. A new quantitative model of plasma‐mediated ablation is introduced and found to closely predict the observed results. Based on the promising nature of the experimental data further investigations are planned in the use of a mode locked Nd:YLF laser as an alternative to excimer lasers for refractive corneal surgery.
Use of the pulsed Nd:YAG laser for intraoral soft tissue surgery
Authors: White Joel M. , Goodis Harold E. , Rose Charles L.
Published: March 2007

Application of a neodymium:yttrium‐aluminum‐garnet (Nd:YAG) laser was compared to conventional scalpel in dental soft tissue surgery. Two surgery sites on 29 patients were randomly selected and treated. An additional 41 patients were exclusively treated with the Nd:YAG laser. The surgical technique was then evaluated for periodontal pocket depths, degree of pain perceived, bleeding, inflammation, procedure time, and anesthesia. Surgical prognosis was made at the time of surgery and compared to actual healing 1 week and 1 month after surgery.

No differences were observed between laser and scalpel surgery in terms of pocket depth reduction, postoperative pain, postoperative inflammation, and treatment time. However, operative and postoperative bleeding with laser surgery were significantly less than with conventional surgery. Anesthesia is required for scalpel surgery, the majority of laser‐treated sites evoked minimal pain without anesthesia.

These results indicate that the Nd:YAG laser can be used successfully for intraoral soft tissue applications are well tolerated without anesthesia and minimal bleeding compared to scalpel surgery.
Post polymerization strength values of an argon laser cured resin
Authors: Blankenau R. J. , Powell G. L. , Kelsey W. P. , Barkmeier W. W.
Published: March 2007

A hybrid composite resin, Prisma APH, and a microfilled composite resin, Silux Plus, were compared regarding diametral tensile strength values following conventional visible light polymerization and argon lasing. The time interval between resin polymerization and physical property testing ranged from 1 hour to 20 days. Results demonstrated considerable mean tensile strength value variation in the earlier phases of the study with a lessening of the differences between the tensile strengths achieved by each method of polymerization as the 20 day interval was approached. It was concluded that composite resin testing protocols should be lengthened to be able to fully assess the effects of the widely variant, time dependent mean test results.
Laser‐assisted microvascular anastomosis using CO2 and KTP/532 lasers
Authors: Samonte Bernadette R. , Fried Marvin P.
Published: March 2007

The milliwatt carbon dioxide (CO2) laser has been shown to be an effective device for performing laser‐assisted microvascular anastomosis (LAMA) with consistently high patency rates, minimal tissue disruption, and rapid surgical time as well as the potential for reduced inflammation due to fewer foreign bodies (sutures) in the wound. The purpose of this investigation was to determine the feasibility of using the potassium titanyl phosphate (KTP) laser to perform LAMA and to compare it to CO2 LAMA in both arteries and veins. Patency rates, inflammatory response, and course of healing were evaluated through histological analysis.

Twenty‐eight rats were divided into two groups, which underwent either CO2 or KTP LAMA and then were sacrificed at 3 days, and 1, 2, 4, 8, and 12 weeks postoperatively. Patency rates for arteries and veins were comparable for both wavelengths (CO2: 100% for arteries, 93% for veins; KTP: 93% for arteries, 93% for veins). Histological grading of inflammation and fibrosis showed no significant difference between the two groups.

This study demonstrated the efficacy of using the KTP/532 laser in performing LAMA. We found the KTP and CO2 LAMA to have comparable patterns of tissue damage and course of healing. Although this experiment did not investigate the mechanism(s) of tissue welding, our results suggest that successful LAMA may be independent of wavelength.
Alternative lasers for endoscopic surgery: Comparison of pulsed thulium‐holmium‐chromium:YAG with continuous‐wave neodymium:YAG laser for ablation of colonic mucosa
Authors: Bass Lawrence S. , Oz Mehmet C. , Trokel Stephen L. , Treat Michael R.
Published: March 2007

Precise and controllable tissue vaporization is essential for minimizing risk in removal of sessile polyps from the lumen of thin walled gastrointestinal organs such as the colon. We compared the ablative efficiency on canine colonic mucosa of the THC:YAG laser with the clinically employed cw Nd:YAG laser. Fresh canine colon was treated with a progressive dose schedule using each laser at several enery/power densities. Ablation depth was measured on fresh tissue and thermal (non‐ablation or coagulative) damage examined histologically. The THC:YAG ablation rates were 13.7 ± 0.8 and 10.2 ± 0.4 μm/J at 55 and 85 J/cm2, respectively. The Nd:YAG laser generated 3.7 ± 0.3, 2.8 ± 0.1, and 3.6 ± 0.2 μm/J at 4,460, 5,095, and 5,730 W/cm2, respectively. There was a significant (P< 0.001) difference among the THC:YAG ablation rates and between the THC: YAG and Nd:YAG ablation rates (ANOVA). The THC:YAG laser craters had significantly less collateral thermal damage than Nd:YAG. The pulsed THC:YAG laser should have an important clinical role since its use could reduce the risk of perforation in endoscopic laser procedures such as the removal of sessile polyps.