bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractPhotokilling 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

AbstractWe 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

AbstractThermal 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

AbstractA 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

AbstractPhotodynamic 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

AbstractThe 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

AbstractIn 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

AbstractCell 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

AbstractThe 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

AbstractTemperature 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractLaboratory 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

AbstractPulsed 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

AbstractThermal 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

AbstractAlbino 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.