bluuebunny/crossref_metadata_2025 huggingface dataset:
Excimer laser corneal ablation: Absence of a significant “incubation” effect
Authors: Pettit G. H. , Ediger M. N. , Weiblinger R. P.
Published: March 2007

Pulse‐to‐pulse consistency of excimer laser etching of cornea has been examined via two noncontact techniques: photoacoustic probe beam deflection, and time‐resolved excimer pulse reflectometry. These methods clearly document the incubation phenomenon accompanying excimer laser ablation of polymethylmethacrylate and the absence of the effect during polyimide ablation. In comparison, results for corneal ablation indicate consistent tissue etching over a train of pulses. Consequently, incubation appears to have negligible impact on corneal ablation.
Hyperthermia potentiates the effects of aluminum phthalocyanine tetrasulfonate‐mediated photodynamic toxicity in human malignant and normal cell lines
Authors: Glassberg Edward , Lewandowski Lawrence , Halcin Cynthia , Lask Gary , Uitto Jouni
Published: March 2007

The purpose of this study was to examine the effects of photodynamic therapy utilizing aluminum phthalocyanine tetrasulfonate in vitro on several human malignant and normal cell types, with or without hyperthermia. Cells examined included normal skin fibroblasts, HT‐1080 fibrosarcoma cells, SCC‐25 (squamous cell carcinoma) and malignant melanoma cells. An argon‐pumped continuous wave tunable dye laser at 675 nm was used as the light source, hyperthermia groups were heated to 42.5°C, and radioisotope incorporation was used to measure DNA and protein synthesis as toxicity assays. Results showed an energy‐dose, and AlPcS‐concentration dependent toxicity in all cell lines examined, with moderate selectivity toward malignant cells. Hyperthermia lone was slightly toxic in melanomas and HT‐1080 cell lines but had no effect in normal fibroblasts or SCC‐25 cells. Hyperthermia synergistically potentiated the effects of PDT in all cell lines, and the combined modality was significantly more toxic in all malignant cell lines compared with normal cells. Thus, addition of hyperthermia to PDT protocols may enhance the efficacy of this treatment modality in vitro.
Internal sclerostomy with laser: A new approach to glaucoma surgery
Authors: Melamed Shlomo , Neumann Doron
Published: March 2007

The creation of a fistula that permits controlled flow of aqueous from the anterior chamber to the subconjunctival space has been and remains the main technical goal of glaucoma filtering surgery. Currently, most complications are secondary to the surgical manipulation of the conjunctiva (mainly leakage from bleb and conjunctival fibrosis) or flattening of the anterior chamber. To overcome this problem, new methods are evolving in which the fistula is created from within the eye, with no conjunctival dissection. The performing of the sclerostomy by means of externally delivered laser energy is a further step in the same direction.
Selectivity, efficiency, and surface characteristics of hard dental tissues ablated with ArF pulsed excimer lasers
Authors: Neev Joseph , Liaw Lih‐Huei L. , Raney Dan V. , Fujishige Jack T. , Ho Peter D. , Berns Michael W.
Published: March 2007

Lasers are finding expanding applications in the field of dentistry. Cutting in soft tissue, hard dental material ablation, caries removal, and root canal therapy are only a few examples of dental laser uses.

In this article, the application of short pulse ArF excimer laser to ablation of dentin and enamel is investigated. In particular, the effect of laser pulse repetition rates (PRR) and fluence levels on the efficiency of the ablation process and on the average thermal response of ablated surfaces is investigated.

Ablation of dentin was found to be considerably more efficient than the ablation of enamel and depends exponentially on the laser fluence. Both dentin and enamel surfaces showed an increase in surface temperature with repetition rate. At lower PRR, however, temperature increases are very small. Surface temperature was also found to increase with laser fluence, although this increase is very small at laser PRR of 5 Hz or less. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage.

Microscopic examination of the ablated surface shows no crack formation, charring, discoloration, or any other thermal damage. The ablated surfaces appear to be very smooth, highly polished, and glossy looking as if they were subjected to thermal melting. This observation is indeed confirmed under scanning electron microscopy (SEM), where evidence of localized melting of the tissue is observed. Furthermore, a close SEM examination of the dentin surface reveals a selectively ablated intertubular dentin, while the remaining pillar‐like dentin tubules are sealed off with fused peritubular dentin.

At all fluence levels and PRR, the first three to four pulses impinging on an untreated enamel surface produced unusually large plumes of debris which were different in size, texture, and fluorescence emission characteristics from the ablation products of subsequent pulses. It is believed that these different ablation characteristics are a consequence of the pulsed ArF laser's ability to selectively remove residual matter from the more resistant enamel surface.
Comparison of tissue effects with sculptured fiberoptic cables and other Nd:YAG laser and argon laser treatments
Authors: Shirk Gerald J. , Gimpelson Richard J. , Krewer Keith
Published: March 2007

The use of a fiber optic cable in contact with tissue results in a complex thermal interaction between the cable and the tissue. The effect of the laser‐tissue interaction was investigated using sculptured quartz fiber optic cables, sapphire contact rods, and bare fiber optic cables attached to the Nd:YAG laser. The laser‐tissue effects of the Nd:YAG and argon lasers were compared. Examination of treated animals showed there to be a significant difference between immediate and 48‐hour thermal effects. The sculptured fibers created significantly less tissue damage than the sapphire contact tips, the 0.6‐mm bare fiber, or the argon laser with a 0.3‐mm bare fiber either with or without contact. All Nd:YAG laser contact treatments were less damaging than the argon laser treatments.
Monitoring myocardial reperfusion injury with NADH fluorometry
Authors: Horvath Keith A. , Torchiana David F. , Daggett Willard M. , Nishioka Norman S.
Published: March 2007

Using NADH fluorometry to monitor myocardial metabolism, the mechanism of reperfusion injury was investigated after the delivery of an experimental reperfusate. Using an isolated working heart preparation, rat hearts underwent 15 min of global ischemia at 37°C. Following the ischemic insult, an oxygenated enriched reperfusion solution was given for 5 min. The hearts were then returned to a working state and aortic flow recorded to evaluate recovery. NADH levels were monitored throughout the experiment with a fluorometer and glycogen, AMP, ADP, and ATP were measured biochemically pre‐ and postischemia, after reperfusion and after recovery. In this study, reperfusion injury was best abated by an enriched reperfusate. Our results indicate the mechanism for this amelioration is not high‐energy phosphate replenishment. Rather, as indicated by NADH fluorescence, the hearts attain an intermediate level of metabolism that permits glycogen to be restored and functional recovery to be improved.
Transurethral laser prostatectomy in the canine model
Authors: Kandel Laurence B. , Harrison Lloyd H. , McCullough David L. , Woodruff Ralph D. , Dyer Raymond B.
Published: March 2007

A technique for performing transurethral prostatectomy was devised using a Neodymium:Yttrium Aluminum Garnet laser in a canine model. Six dogs underwent transurethral laser prostatectomy following establishment of a perineal urethrostomy. The efficacy of the prostatectomies was judged by retrograde urethrography, transrectal prostate ultrasonography, cystoscopy, and histologic examination. The method of applying laser energy while holding the tip of the fiberoptic light guide 2–3 mm away from the prostate was ineffective; with power ranging from 40 to 70 watts, this technique resulted mainly in coagulation necrosis and removal of only a small amount of tissue. However, placing the tip of the light guide in direct contact with the prostate and using power from 70 to 100 watts produced impressively large prostatectomy defects by tissue vaporization. We conclude that this newly devised technique for transurethral prostatectomy in the canine model can be performed safely and effectively using a Neodymium: Yttrium Aluminum Garnet laser (Neodymium:YAG).
Microbeam laser‐injured neurons increase in vitro astrocytic gap junctional communication as measured by fluorescence recovery after laser photobleaching
Authors: Anders Juanita J. , Woolery Sara
Published: March 2007

An important aspect of the neuronal–astrocyte relationship is the interaction of reactive astrocytes with injured and/or dying neurons. Few studies have focused on the signaling of astrocytes by injured neurons or on the possibility that neurons can alter as‐trocytic gap Junctional communication. The purpose of this study was to determine whether the presence of injured neurons could alter astrocytic gap Junctional coupling by establishing an in vitro method of microbeam laser neuronal injury and coculturing these neurons with astrocytes. Neurons from two rat neuronal clonal cell lines were injured using a 20‐W argon laser operating on the ultraviolet (UV) multiline (351–361 nm) directed through a X40 objective of an inverted microscope. After laser injury, the glass slide with the injured neurons was sandwiched with a slide on which primary rat astrocytes were grown. Although the neurons and astrocytes were bathed in the same medium, they were not in direct contact during the coculture period (24,48, or 72 hr). Astrocytic gap Junctional dye coupling was examined using the fluorescence recovery after laser photobleaching (gap‐FRAP) analysis technique. Astrocytes cocultured with the injured neurons for 24 to 48 hr did not show a significant difference in fluorescence recovery when compared to control values. After 72 hr of coculture, there was a significant increase in the gap Junctional dye coupling. These results indicate that injured neurons influence in vitro astrocytic gap Junctional conductance after 72 hr of coculture as measured by dye coupling.
Histologic evaluation of rat mammary tumor necrosis by interstitial Nd:YAG laser hyperthermia
Authors: Dowlatshahi Kambiz , Babich Debra , Bangert Julee D. , Kluiber Rudolph
Published: March 2007

The extent of coagulative necrosis caused by interstitial laser hyperthermia was measured for different quantities of laser energy in a rat mammary tumor model. Continuous wave Nd:YAG laser at a power level of 5 W was focused onto a 600 JA diameter bare tip quartz fiber and placed inside a 19‐gauge needle, which allowed the para‐axial flow of normal saline at 1 cc/min. A microthermocouple soldered to the outside of the probe continuously provided the interstitial temperature. After the probe was inserted into the tumor, it was withdrawn as laser energy was administered at a rate sufficient to maintain the temperature within 42–45°C. Tumors were excised after 48 hours, fixed in formalin, cut in 3 mm slices, and the coagulated surfaces measured microscopically. Laser fiber transmission loss was 1% per 1,000 J of laser energy and the average time required to coagulate 1 cc of tumor was 2 minutes. There was a statistically significant correlation between the volume of tumor necrosis and the level of laser irradiation (r = 0.71, P<0.001). It is concluded that the described technique is an efficient method of tumor coagulation by interstitial laser hyperthermia and proportionally larger volumes of necrosis are created with greater amounts of laser energy. © 1992 Wiley‐Liss, Inc.
CO2 laser annular thermokeratoplasty: A preliminary study
Authors: Chandonnet Alain , Bazin Richard , Sirois Claude , Bélanger Pierre‐André
Published: March 2007

Since most techniques of refractive surgery currently in use or being developed have the potential for significant side effects, there is a need for investigating alternative procedures. We herein report on the use of a pulsed CO2 laser beam delivered through a pair of complementary axicons to produce a ring of stromal collagen contraction resulting in the flattening of the corneal apex of cadaver eyes. Irradiances of 29 W/cm2 and 23 W/cm2 were used for rings of 5.5 mm and 7.0 mm, respectively. The creation of a ring of 7.0 mm in diameter did not affect the corneal curvature significantly but when the diameter was reduced to 5.5 mm, substantial flattening proportional to the dose of radiation took place. In our system, it was possible to achieve up to 11.3 diopters of mean keratometry flattening (90 joules, 5.5 mm of diameter). In addition, a 1 mm posterior displacement of the corneal dome without histological evidence of closure of the iridocorneal angle was observed. Annular thermokeratoplasty (ATK) may minimize side effects encountered with other refractive procedures since it does not require ablation, incisions, or interaction with the central optical zone. © 1992 Wiley‐Liss, Inc.
Pulse duration effects on cutaneous pigment
Authors: Kurban Amal K. , Morrison Paul R. , Trainor Shawn W. , Tan Oon T.
Published: March 2007

Melanin, an endogenous chromophore in pigment containing cells in skin, is being specifically altered by lasers using the principle of selective photothermolysis (SPT). This implies that a combination of specific laser parameters of wavelength, pulse duration, spotsize, and energy density are required to confine the delivered laser energy to the targeted cells alone. Because the bulk of cutaneous pigment is localized to epidermal basal cells, pigmentary incontinence has been found to occur in skin exposed to laser irradiation. This study demonstrates that pulse duration or exposure time of the laser affect the severity of pigmentary incontinence induced. Pigment granules are more abundant, aggregated, and located deeper in the dermis following exposure to 500 nsec pulse duration than 100 nsec at a wavelength of 504 nm. This relationship appears to be independent of the laser energy density used. © 1992 Wiley‐Liss, Inc.
Massive air embolism complicating Nd‐YAG laser endobronchial photoresection
Authors: Golish Joseph A. , Pena Cesar M. , Mehta Atul C.
Published: March 2007

A 63 year old male underwent 6,900 rads of external radiation for a squamous cell carcinoma of the left main bronchus. Recurrence of the tumor 8 months later was treated with 6,618 joules and patency of the left main bronchus was restored. Four months later, he developed complete atelectasis of the left lung requiring repeat laser. During the procedure he became hypotensive, bradycardic, and hypoxic due to a tension pneumothorax. Although treated promptly with thoracostomy tube drainage, the patient never awakened. CT scan of the brain demonstrated anoxic encephalopathy with air present in the right frontal lobe. Brain death was confirmed by an EEG and cerebral angiogram.

Air embolism has been reported in conjuction with diagnostic procedures including therapeutic pneumothorax for tuberculosis, transthoracic needle biopsy of the lung, and positive pressure ventilation with or without pneumothorax. The only reported case of air embolism associated with laser was a small middle cerebral artery cerebrovascular accident which was self limited. Its mechanism is unclear, but it is suspected to be due to a communication between a pulmonary vein and the atmosphere. A greater volume of air will enter the damaged vessel in the setting of positive pressure ventilation and/or a tension pneumothorax. When neurologic manifestations are present, hyperbaric oxygen therapy is the treatment of choice. Prompt institution in hemodynamically stable patients can minimize neurologic sequelae. © 1992 Wiley‐Liss, Inc.
Photoacoustic injury and bone healing following 193nm excimer laser ablation
Authors: Lustmann Joshua , Ulmansky Mario , Fuxbrunner Amihay , Lewis Aaron
Published: March 2007

The argon‐fluoride excimer laser was investigated as a cutting‐ablating tool for bone surgery. A total of 52 rats were divided into two experimental groups and two control groups. In one experimental group cortical bone defects were made; in another experimental group defects penetrating into the medullary space were performed. In the two control groups similar defects were achieved using water‐cooled carbide burs. The rats were sacrificed on each of the 3, 7, 10, 20, 30, and 40 postoperative day. The cortical bone, the medullary space, and the extrabony tissue were examined by means of light microscopy. In both experimental groups, bone damage, represented by osteocyte destruction, extended to 1,050–1,450 μm ahead from the irradiated site, and bone healing was very much impaired. In the control groups no histological changes could be identified and bone healing appeared to be within normal limits. We believe this extensive bone damage, following 193 nm irradiation, to be a result of photoacoustic waves propagating in the bone following each pulse. In view of our results we feel that excimer lasers presently in use are not suitable for bone surgery. This problem of photoacoustic damage can be overcome in one of two ways: by designing a CW excimer laser or by reducing the pulse width to the picosecond regime. © 1992 Wiley‐Liss, Inc.
Effects of coaxial CO2/Nd:YAG irradiation on periodontal wound healing
Authors: Arcoria Charles J. , Steele Robert E. , Vitasek Bunny A. , Wagner Martin J.
Published: March 2007

This study evaluated a coaxial CO2/Nd:YAG laser used during periodontal surgery in mongrel dogs for the purpose of ablating the osseous portions of root surfaces to increase reattachment of soft tissue. Periodontal defects were produced with ligatures of orthodontic wire and elastics. The left mandibular osseous root surfaces were irradiated with a defocused, CW laser beam [power density (PD) = 42.46 W/cm2, energy density (ED) = 424.63 J/cm2]. The left maxillary osseous root surfaces were treated with a beam at twice the energy density [PD = 84.93 W/cm2, ED = 849.3 J/cm2]. The mandibular right quadrant received conventional surgery and the maxillary right quadrant served as the untreated control. Fourteen days after treatment, facial/lingual attached gingivae were scored for soft tissue adherence to bone. Laser irradiation at low ED did not improve soft tissue attachment when compared to conventional treatment. Higher ED irradiation produced significantly less attachment and increased tissue necrosis. © 1992 Wiley‐Liss, Inc.
Microprocessor‐Controlled Nd:YAG laser for hyperthermia induction in the RIF‐1 tumor
Authors: Waldow Stephen M. , Russell Gail E. , Wallner Paul E.
Published: March 2007

Near‐infrared radiation from a Nd:YAG laser at 1,064 nm was used interstitially or superficially to induce hyperthermia in RIF‐1 tumors in C3H male mice. A single 600‐μm quartz fiber with a 0.5‐cm cylindrical diffusor or a weakly diverging microlens at its distal end was used to deliver laser energy to tumors in the hind leg (mean volume = 100 mm3). Two thermocouples were inserted into each tumor. One thermocouple controlled a microprocessor‐driven hyperthermia program (maximum output of 3.5 Watts) to maintain the desired temperature. Tumors were exposed to various temperature‐time combinations (42–45°C/30 min). Our initial results indicated that excellent temperature control to within 0.2°C of the desired temperature at the feedback thermocouple was achievable during both superficial and interstitial heat treatments. Temperatures at the second thermocouple, however, were found to be lower by as much as 2.3°C (using the cylindrical diffusor) or higher by up to 4.6°C (using the microlens) when compared to the feedback thermocouple temperature. Several correlations were seen between total dose, tumor growth delay, percent skin necrosis, and temperature at the second thermocouple after several superficial and interstitial treatments. Statistically significant improvements in tumor growth delay (at 42 and 45°C) and increased percent skin necrosis at all temperatures were observed after superficial versus interstitial treatment. © 1992 Wiley‐Liss, Inc.
Comparison of holmium and flashlamp pumped dye lasers for use in lithotripsy of biliary calculi
Authors: Spindel Mitchell L. , Moslem Ali , Bhatia Kuldip S. , Jassemnejad Bahaeddin , Bartels Kenneth E. , Powell Richard C. , O'Hare Ciaran M. , Tytle Tim
Published: March 2007

The characteristics of laser lithotripsy of biliary calculi are compared for a flashlamp pumped dye laser (λ = 640 nm) and a Cr: Tm:Ho‐YAG laser (λ = 2.1 μm). Data on fragmentation efficiency with respect to laser power and pulse repetition rate are presented for different types of stones. It is shown that both lasers can produce effective stone fragmentation. The laser power required for efficient fragmentation characteristics is significantly less for the visible wavelength laser. However, the problems associated with damage to the fiber tips of the delivery system during operation were found to be less with the near infrared wavelength. The laser power for efficient fragmentation with the dye laser varies significantly for different types of stones while the power for efficient fragmentation with the hohnium laser is the same for all stones. © 1992 Wiley‐Liss, Inc.
Treatment of distal ureteral tumors using endoscopic argon photoirradiation
Authors: Johnson Douglas E.
Published: March 2007

This is the first report on the use of endoscopic argon photoirradiation to treat patients with low‐grade ureteral tumors involving the distal ureter. Using a rigid ureteropyeloscope, a 300 μ, or 600 μ quartz fiber, and 5 watts (W) of power in a continuous‐wave mode, the lesions were ablated without complication. Patients remain free of ureteral recurrence after 5, 7, and 22 months. We conclude that the shallow (1 mm) depth of penetration and the ability to use the fiber in either a contact or noncontact mode provide the surgeon a large margin of safety and low risk of ureteral perforation. © 1992 Wiley‐Liss, Inc.
Changes in type I collagen following laser welding
Authors: Bass Lawrence S. , Moazami Nader , Pocsidio Joanne , Oz Mehmet C. , Logerfo Paul , Treat Michael R.
Published: March 2007

Selection of ideal laser parameters for tissue welding is inhibited by poor understanding of the mechanism. We investigated structural changes in collagen molecules extracted from rat tail tendon (> 90% type I collagen) after tissue welding using an 808 nm diode laser and indocyanine green dye applied to the weld site. Mobility patterns on SDS‐PAGE were identical in the lasered and untreated tendon extracts with urea or acetic acid. Pepsin incubation after acetic acid extraction revealed a reduction of collagen alpha and beta bands in lasered compared with untreated specimens. Circular dichroism studies of rat tail tendon showed absence of helical structure in collagen from lasered tendon. No evidence for covalent bonding was present in laser‐treated tissues. Collagen molecules are denatured by the laser wavelength and parameters used in this study. No significant amount of helical structure is regenerated on cooling. We conclude that non‐covalent interactions between denatured collagen molecules may be responsible for the creation of tissue welding. © 1992 Wiley‐Liss, Inc.
XeCl laser ablation of atherosclerotic aorta: Optical properties and energy pathways
Authors: Oraevsky Alexander A. , Jacques Steven L. , Pettit George H. , Saidi Iyad S. , Tittel Frank K. , Henry Philip D.
Published: March 2007

The energetics of 308‐nm excimer laser irradiation of human aorta were studied. The heat generation that occurred during laser irradiation of atherosclerotic aorta equaled the absorbed laser energy minus the fraction of energy for escaping fluorescence (0.8–1.6%) and photochemical decomposition (2%). The absorbed laser energy is equal to the total delivered light energy minus the energy lost as specular reflectance (2.4%, air/tissue) and diffuse reflectance (11.5–15.5%). Overall, about 79–83.5% of the delivered light energy was converted to heat. We conclude that the mechanism of XeCl laser ablation of soft tissue involves thermal overheating of the irradiated volume with subsequent explosive vaporization. The optical properties of normal wall of human aorta and fibrous plaque, both native and denatured were determined. The light scattering was significant and sufficient to cause a subsurface fluence (J/cm2) in native aorta that equaled 1.8 times the broad‐beam radiant exposure, Φo (2.7Φo for denatured aorta). An optical fiber must have a diameter of at least 800 μm to achieve a maximum light penetration (≈200 mu;m for μo/e) in the aorta along the central axis of the beam. © 1992 Wiley‐Liss, Inc.
Effects of rapid pulsed CO2 laser beam on cortical bone in vivo
Authors: Rayan Ghazi M. , Stanfield Denver T. , Cahill Sandy , Kosanke Stanley D. , Kopta Joseph A.
Published: March 2007

Twenty rabbit femurs were used to study the effect of CO2 laser on cortical bone. Sixteen femurs were treated with 20 watts, 3 mm defocused beam, 2 KHZ spike pulse mode CO2 laser for 10 seconds through a circular window in the metaphysis. In four control femurs, the inner cortex was exposed without laser treatment. The animals were killed at 4 and 6 weeks and the specimens studied histologically. All laser‐treated specimens showed thermal changes. Three histological zones were observed. A superficial zone of inner cortex close to the beam consisted mainly of carbonization or carbon ash during resorption. An intermediate zone consisted of bone necrosis and healing with associated areas of new bone formation. The deep zone of outer cortex had normal bone with no cellular damage. No such changes were observed in the control specimens. The CO2 laser can be used to generate a controlled zone of tissue ablation, which may make it a potentially useful tool for tumor margin cauterization. © 1992 Wiley‐Liss, Inc.
Clinical application of the Nd:YAG laser bipolar dissector in intra‐abdominal surgery
Authors: Nishiwaki Yoshiro , Daikuzono Norio , Joffe Stephen N.
Published: March 2007

A laser bipolar dissector (LBD) using a 1064 nm Nd:YAG laser energy source that provides hemostatic dissection using lowpowered laser energy (15–25 W) has been developed. Clinical applications have included a partial hepatectomy (n = 5), a cholecystectomy (n = 4), an appendectomy, lymphnode dissection, and division of adhesions. The LBD was effective in resection of noncirrhotic liver and reduced the number of ligations required. There were no direct complications related to using the LBD. Operative time and blood loss were difficult to compare to conventional methods. The LBD may have applications for partial hepatectomies and other intra‐abdominal operations. © 1992 Wiley‐Liss, Inc.
Interstitial laser photocoagulation: Nd:YAG 1064 nm optical fiber source compared to point heat source
Authors: Wyman D. R. , Whelan W. M. , Wilson B. C.
Published: March 2007

Interstitial laser photocoagulation (ILP) was performed in vitro in lean bovine and chicken muscle by delivering 1.6 W of continuous‐wave Nd:YAG laser energy (1064 nm) from a 400‐μm core optical fiber for 300s. The resulting thermal coagulation lesion was consistently larger when the delivered energy was deposited into a small steel sphere than when it was delivered freely into the tissue. Mathematical modelling confirms this result. This preliminary study suggests that a point heat source produces a larger volume of thermal coagulation than a point optical source (1064 nm) delivering the same power. © 1992 Wiley‐Liss, Inc.
Laser‐induced hyperthermia: Comparison of two different methods
Authors: Castrén‐Persons Maaret , Lipasti Jarmo , Puolakkainen Pauli , Schröder Tom
Published: March 2007

The effectiveness of two different techniques of laser‐induced hyperthermia was analyzed in healthy piglet livers. Hyperthermia was produced using a continuous‐wave Nd:YAG laser with both a contact sapphire probe and a bare quartz fibre. In both methods the tip was inserted into the liver, and the temperature 1 cm from the tip was raised and held between 42°C and 44°C for 600 seconds. Specimens were taken 0, 7 and 14 days after the treatment. The tissue effects of 36 treatment sites were analysed using standard van Gieson's method. In addition, a histochemical method for demonstrating lactate dehydrogenase activity was employed to show damage not observable by routine methods. No statistically significant difference in the extent of the treatment sites at d 0 and after 7 days was seen when comparing the two laser methods. After 2 weeks, the diameter of the lesion with the bare fibre was significantly larger (3,7 mm with both analysing methods) than by using the contact probe (2,6 with LDH demonstration; P < 0.01 and 2,1 mm with van Gieson's staining; P < 0.001). It can be concluded that the simple fibre tip seems more effective in causing tissue necrosis than the sapphire tip. © 1992 Wiley‐Liss, Inc.
Photoinhibition of smooth muscle cell migration: Potential therapy for restenosis
Authors: Deckelbaum Lawrence I. , Scott John J. , Stetz Mark L. , O'Brien Kenneth M. , Sumpio Bauer E. , Madri Joseph A. , Bell Leonard
Published: March 2007

Evidence from animal, autopsy, and atherectomy studies demonstrates that migration and proliferation of smooth muscle cells of medial origin result in neointima formation and decreased luminal cross‐sectional area. The purpose of this study was to evaluate whether low energy light irradiation can inhibit smooth muscle cell migration and therefore potentially reduce the degree of neointima formation and the incidence of restenosis. The migration kinetics of bovine aortic smooth muscle cell monolayers were examined using a fence assay. The effect on smooth muscle cell migration of irradiation with monochromatic light at wavelengths ranging from 400 to 700 nm was compared to the migration of cells irradiated with broadband white light or maintained in the dark. Wavelength specific photoinhibition of smooth muscle cell migration was observed; 594–600 nm light reproducibly inhibited migration by 12–29% (P < 0.05). Migration rate was significantly reduced following daily radiant exposures of 1.0 J/cm2 as well as following a single radiant exposure of 0.09 or 0.9 J/cm2. The decrease in migration was not associated with any change in cell proliferation or [3H] thymidine incorporation. We conclude that 594–600 nm light inhibits smooth muscle cell migration in vitro and may potentially be used in vivo to decrease fibrointimal thickening following arterial injury. This application of photoinhibition may be useful in retarding restenosis following angioplasty. © 1993 Wiley‐Liss, Inc.
Optical properties of rat liver and tumor at 633 nm and 1064 nm: Photofrin enhances scattering
Authors: van Hillegersberg Richard , Pickering John W. , Aalders Maurice , Beek Johan F.
Published: March 2007

Predicting the effects of photodynamic therapy (PDT) and Nd: YAG laser coagulation requires knowledge of the light distribution in tumor and surrounding tissue. Therefore, absorption and scattering coefficients and the average cosine of the scattering angle (the anisotropy factor) were measured in rat liver and tumor at 632.8 and 1064 nm. A syngenic colon adenocarcinoma CC531 was implanted subcutaneously in two groups of 7 Wag/Rij rats. In one group Photofrin was administered 5 mg/kg intravenously 48 h before determination of optical properties. Two months after inoculation, samples were taken from tumor and liver and optical properties determined using indirect methods with two integrating spheres. The absorption coefficient was larger in liver than in tumor at 632.8 nm (P < 0.0005), whereas the scattering coefficient was larger in tumor than in liver at 1,064 nm (P < 0.05). Addition of Photofrin increased the scattering coefficient in liver and in tumor at both wavelengths (P < 0.025) and decreased the anisotropy in tumor (P < 0.025), suggesting that for modelling the dosimetry of PDT the optical properties of photosensitized tissue should be used. © 1993 Wiley‐Liss, Inc.
Effects of ArF: Excimer laser irradiation on human enamel and dentin
Authors: Arima Mari , Matsumoto Koukichi
Published: March 2007

Round enamel and dentin surfaces of sound and carious extracted human teeth were irradiated by an ArF:excimer laser for up to 180 sec. Thermographic measurements indicated that the temperature rise due to heat accumulation caused by laser irradiation on these enamel and dentin surfaces was up to 19°C (10 HZ with 540 J/cm2), and the temperature returned to the preirradiation value within 10 sec after the irradiation was stopped. Under light microscopy, no carbonization was evident on these surfaces, and a simple recess was formed by abrasion or vaporization in the irradiated regions. In the secondary SEM, uniformly distributed fine pores and prism structures appeared slightly on the enamel surfaces. Between the peritubular and the intertubular dentin, there appeared a distinct difference in the dissolved area. The laser almost completely removed carious regions of the enamel and the dentin, and penetration extended beyond the carious regions. In the backscattered electron SEM, highly mineralized layers were observed on the enamel and dentin surfaces dissolved by the laser. © 1993 Wiley‐Liss, Inc.
Preliminary analysis of histological results of Hexascan™ device with continuous tunable dye laser at 514 (argon) and 577 NM (yellow)
Authors: Apfelberg David B. , Smoller Bruce
Published: March 2007

This histological study demonstrates that the Hexascan™ device combined with a continuous tunable dye laser at either 514 nm or 577 nm is able to effectively treat port wine hemangiomas. Both 514 nm and 577 nm were effective in producing almost normal looking skin histologically after treatment in some patients. Other patients demonstrated a minor number of residual vessels or no significant change. In this small series, it appeared that the 514 nm and 577 nm wavelengths were similar histologically. © 1993 Wiley‐Liss, Inc.
Pulsed dye laser treatment of recalcitrant verrucae: A preliminary report
Authors: Tan O. T. , Hurwitz R. M. , Stafford T. J.
Published: March 2007

Patients with recalcitrant warts on the fingers and hands, periungual, and other parts of the body including verrucae plana and plantar surfaces were treated using the pulsed dye laser at 585 nm, 450 usec, and a spotsize of 5 mm diameter. Of the 39 patients treated, 28 (72%) were cleared of their warts after an average of 1.68 treatments at fluences of 6.25–7.5 J/cm2. Seven (18%) patients had a reduction of between 80–95% of their warts after 1.3 treatments, and verrucae reduced by 50% in four of the 39 patients after one treatment. The average follow‐up period of the 28 cases cleared of their warts has been 5 months. Of this group, those with periungual warts have been followed for up to 6.4 months, compared to 4.8 months for those with warts on other parts of their body, 4.0 months for those with finger and hand warts, and 2.0 months for plantar warts. Only one of the 28 patients has had a recurrence after 3 months of clearance. © 1993 Wiley‐Liss, Inc.
Preliminary experience with transluminal laser–induced intrahepatic portacaval shunts
Authors: Cikrit Dolores F. , Wadley J. Jeffrey , Harl Michael J. , Heller Sherry A. , Dalsing Michael C.
Published: March 2007

This study investigated the feasibility of performing an intrahepatic portacaval shunt (IHPCS) by means of transluminal laser angioplasty. In 10 anesthized dogs, a catheter was introduced into a mesenteric vein and threaded into the portal vein (PV). Under fluoroscopy, a Ross needle was passed through the PV catheter, liver, and into the intrahepatic IVC. Following guidewire exchange, a neodymium YAG laser hot‐tip probe (power setting 8 W) was passed over the guidewire to accomplish a transluminal IHPCS. In five animals, an IHPCS could not be accomplished. Initial and subsequent patency was confirmed by fluoroscopy. These early data suggest that transvenous laser‐in‐duced intrahepatic portacaval shunts may be feasible as a means of decompressing portal hypertension. Further research is necessary to investigate the long‐term patency as well as this technique's ability to decompress the portal system. © 1993 Wiley‐Liss, Inc.
Modeling the color perception of port wine stains and its relation to the depth of laser coagulated blood vessels
Authors: Lakmaker Olof , Pickering John W. , van Gemert Martin J. C.
Published: March 2007

To find the maximal depth of an ectatic vessel in the dermis that contributes to the abnormal color of a port wine stain (PWS), “normal” and “laser treated PWS skin” are modeled, respectively, as a two‐layer plane parallel geometry consisting of an epidermis and a dermis, and as a three‐layer geometry consisting of an epidermis, a dermis without additional blood (the “treated” part of the stain, assumed identical to the “normal” dermis), and a layer of dermis containing 5% or 10% of blood per volume (the untreated part of the PWS). Spectral remittances were calculated for various wavelengths using the diffusion approximation to the transport equation for light propagation. These remittances were transformed into the CIE 1976 (L*a*b*)‐color system. Color differences between “normal” and PWS skin as a function of the dermal depth of “injured” ectatic blood vessels were calculated. The maximal depth where ectatic blood vessels just contribute to the abnormal PWS color is predicted as 0.9 mm for a “normally” pigmented epidermis (60 μm thick) and a 5% or 10% blood per volume content. For a darker pigmented epidermis (60 μm thickness) and again at both 5% and 10% blood per volume content, this depth was found to be 0.8 mm. © 1993 Wiley‐Liss, Inc.
600 nm flash pumped dye laser for fragile telangiectasia of the elderly
Authors: Goldman Leon , Kerr James H. , Larkin Marcus , Binder Scott
Published: March 2007

Since 1984, a continuum of controlled studies have been done on the use of the fragile, superficial telangiectasia of the elderly, which were utilized as a model for some of the basic studies of the effects of lasers on the cardiovascular system. We report the use of the 600 nm flash pumped dye laser for the fragile telangiectasia of the elderly in our classification of the Class 2 group. In some vessels studied, the special Teflon‐insulated, intravenous electric needle of Kobayashi‐Yamada was used. For the bluish vessels, the 600 nm flash pumped dye laser penetrated deeper into the vessel than the 585 nm, but multiple and repeated treatments were needed for clinical effect. Preliminary studies have also shown some initial response in port wine marks and facial telangiectasia. © 1993 Wiley‐Liss, Inc.
Occurrence, extent, and implications of pressure waves during excimer laser ablation of normal arterial wall and atherosclerotic plaque
Authors: Haase Karl K. , Hanke Hartmut , Baumbach Andreas , Hassenstein Stefan , Wehrmann Manfred , Duda Stefan , Rose Carsten , von Münch Waldemar , Karsch Karl R.
Published: March 2007

Ablation of atherosclerotic plaque and normal arterial wall was performed using a Xenon‐Chloride Excimer laser with a wavelength of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 μm bare fibre and adjusted to an energy density of 3.5J/cm2. The acoustic signals generated by the laser pulse were measured with two types of hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and 0.5 mm and recorded on a dual channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband fibre‐optic transmission system. Tissue was retrieved from nine cadaver human aortas and macroscopically classified as either normal or calcified atherosclerotic plaque. Histological analysis (Haematoxylin eosin, elastica van Gieson, and immunohistochemical staining) was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For normal arterial wall, maximum peak pressure was 1.28 MPa ± 0.85 MPa, rise time 163 ns ± 43 ns, and pressure increase 8,2k Pa ± 5,4k Pa/ns. For calcified, atheromatous segments, a maximum peak pressure of 2,02 MPa ± 1,16 MPa, a rise time of 69,9 ns ± 25,8 ns, and a pressure increase of 32,3 kPa ± 21,3 kPa/ns was found. Statistical analysis showed a significant shorter rise time (P < 0.0001) and a higher pressure increase (P < 0.0001) for calcified tissue in comparison to normal arterial wall, whereas maximum pressures alone did not allow a differentiation of tissue characteristics. Several hundred kPa are generated during Excimer laser ablation. The results suggest that focal tissue fragmentation is one mechanism of plaque ablation. A differentiation of tissue characteristics is possible by analysis of rise time and pressure increase, potentially providing the possibility of acoustic ablation control. © 1993 Wiley‐Liss, Inc.
Scanning electron microscopy and thermal characteristics of dentin ablated by a short‐pulse XeCl excimer laser
Authors: Neev Joseph , Stabholtz Adam , Liaw Lih‐Huei L. , Torabinejad Mahmoud , Fujishige Jack T. , Ho Peter D. , Berns Michael W.
Published: March 2007

The interaction of a short pulse XeCl excimer laser radiation with human dentin was investigated. The dependence of surface temperatures and temperature gradients into the treated teeth on laser parameters such as fluence (0.5J/cm2‐7J/cm2), pulse repetition rate (1Hz‐35Hz), and spot size (0.004cm2‐0.12cm2) was studied. Additionally, the effect of fluence and pulse repetition rate on dentin microstructure was studied using scanning electron microscopy (SEM). It is demonstrated that this “cold ablation” excimer laser can result in significant thermal modification in the dentin surfaces. Changes include the formation of melted dentin grains, which uniformly cover the surface and the exposed dentin tubules. Maximum temperatures of the ablated surfaces, however, remained relatively low at most laser parameters used. Also, the immediate neighborhood of the root canal was essentially undisturbed at most laser parameters. These observations suggest that with the appropriate choice of parameters XeCl lasers can be effective in producing surface structures that may prove useful in enhancing bond strength or other applications in dentistry, without exposing tooth pulp to significant temperature elevation. © 1993 Wiley‐Liss, Inc.
Effects of pulsed lasers on agar model simulation of the arterial wall
Authors: Asada Masakatsu , Kvasnicka Jan , Geschwind Herbert J.
Published: March 2007

Coronary laser angioplasty is limited by a high rate of dissection and the occurrence of abrupt closure and perforation. The aim of this study was to visualize the mechanical effects of pulsed lasers on two chamber in vitro models. These models consisted of 1 or 2 agar layers and calcium carbonate inclusions (1‐layer model) or lipid (2‐layer model) simulating lipid or calcified tissue. The inclusions were irradiated with a holmium‐yttrium‐aluminum‐garnet (Ho‐YAG) laser or a xenon chloride excimer laser. The Ho‐YAG laser demonstrated dissection‐like expansions of the target and perforation‐like cracks. The size of dissection was obtained using an the empirical formula of energy (E) and the maximal expansion distance (Dmax) of the targets, Dmax = 0.15E0,87‐1,17. The excimer laser showed rare and short perforation‐like cracks and little dissection‐like expansion of the gaseous products originating from the ablation of material. Ho‐YAG laser ablation is likely to induce target tissue dissections and/or perforations. Excimer laser ablates targets with less traumatic effects than Ho‐YAG laser. © 1993 Wiley‐Liss, Inc.
Primary closure of choledochotomy using CO2 laser: Comparison with suture closure
Authors: Vanterpool Clyde C. , Gales Morris E. , Bolton Steven , Hawkins Robert P.
Published: March 2007

This study was designed to compare laser welding to suture closure of the common bile duct (CBD). A 12 mm linear choledochotomy was closed in 12 mongrel dogs using tissue welding lowenergy CO2 laser. Tissue welding was accomplished at 5.0 w/cm2 for 120 sec. Twelve similar mongrel dogs (control) were treated with CBD closure using 5/0 Vicryl (polyglactin 910, Ethicon, Inc., Somerville, NJ) interrupted simple stitches. All animals were sacrificed at six weeks. Gross and histologic evaluation of the choledochotomy site were performed. There were no statistical differences in parameters of comparison in the two groups. These parameters were pre‐ and post‐treatment measurements of liver function tests, stenosis, and dehiscence. However, it must be noted that there was a 33% (4/12) incidence of dehiscence and death in the CO2 laser welded choledochorrhaphy. This result, although not statistically significant, is clinically significant. We conclude that the tensile strength of CO2 laser welded CBDs must be optimized and that these results are preliminary and still unreliable to recommend for clinical adaptability. © 1993 Wiley‐Liss, Inc.
Structural changes in dentin induced by high energy, continuous wave carbon dioxide laser
Authors: Shariati Shervin , Pogrel M. Anthony , Marshall Grayson W. , White Joel M.
Published: March 2007

The effect of a continuous wave carbon dioxide laser on dentin was observed as a function of power density and exposure time utilizing a wet scanning electron microscope. Visible charring occurred for all conditions studied. Surface cratering and flaking were followed by melting of the dentin. Melting resulted in a porous layer or porous globules of resolidified material and partial sealing of the tubules. Beneath the melted zone is an area of altered dentin where the tubules appear to be filled by solidification of the melted dentin. © 1993 Wiley‐Liss, Inc.
Use of laser energy to treat central pulmonary emboli: A preliminary report
Authors: Silverman Jeffrey M. , Julien Peter J. , Adler Louis , Fishbein Michael C.
Published: March 2007

We evaluated the ability and safety of a laser fiber placed percutaneously into a pig's lobar pulmonary artery to lyse pulmonary artery blood clots that were created in situ. We developed a model to create blood clots in situ that could be placed in any desired location with a radio‐opaque marker at the clot position. An excimer laser delivered energy to a flexible 600 μm fiber in three experiments and a coaxial 1.6 mm multifiber catheter in the last experiment Pre‐ and postprocedure angiograms obtained from each experiment demonstrated that partial laser dissolution of central pulmonary emboli in four pigs was accomplished successfully. To avoid perforation, it is imperative that the laser fiber remain coaxial during the entire lasing process. These results suggest that laser dissolution may become an adjunctive procedure for the treatment of central pulmonary emboli in those patients who cannot be treated medically. © 1993 Wiley‐Liss, Inc.