bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal characteristics of sapphire contact probe delivery systems for laser angioplasty
Authors: Ashley S. , Brooks S. G. , Gehani A. A. , Kester R. C. , Rees M. R. 
Published: March 2007

AbstractContact probes made from synthetic sapphire crystal, designed for general laser surgery, are currently being evaluated for use in laser angioplasty. Their mode of action and safety in the context of arterial recanalisation is unknown, particularly with respect to the degree of probe and catheter heating. Infrared thermal imaging was used to investigate the surface temperature rise of various rounded sapphire probes during emission of continuous wave Nd‐YAG (1,064 nm) laser energy. Catheter safety was addressed by analyzing the temperature of the metal interface between the optical fiber and sapphire, as well as the catheter proximal to this junction. Transmission of Nd‐YAG energy through each probe was also measured.Five rounded probes of 1.8–3.0 mm diameter (three supplied by Surgical Laser Technologies [SLT], two by Living Technology [LT]), along with their respective optical catheters, were compared. There was a large temperature gradient between the front and rim of the probes. The maximum surface temperature rise of the sapphire (at 20 W, 5‐second exposure) was 314–339°C (SLT) and 90–108°C (LT) [P < 0.00l, 3‐way ANOVA]. The reason for this difference may be related to “crazing” of the front surface of the SLT sapphires. At all energy levels sapphire temperatures were considerably lower than attained by metal laser thermal angioplasty probes. Forward transmission was slightly higher in the SLT probes (75–85%) than the LT sapphires (54‐69%). With fiber perfusion at 2 ml/minute, a minor degree of heating of the metal sapphire holders was recorded (maximum rise 35°C), but heating of the catheter proximal to this was negligible. Therefore, it would appear that the risk of tip detachment or arterial injury due to heating of the connecting metal interface is extremely low. Without perfusion, however, there was a greater degree of interface heating in the LT delivery system suggestive of more laser backscattering by these sapphires compared with the SLT probes [P < 0.00l, one‐way ANOVA]. The SLT system is, therefore, potentially safer in this respect. These results suggest that some degree of surface heating of contact probes due to energy absorption within the sapphire does occur, but is localised to the front of the probe. This effect may contribute to the process of arterial recanalisation with this device. However, variation in the thermal and optical properties of sapphires from different sourceshas been demonstrated. The influence of these properties on plaque ablation, and ultimately the clinical performance of different contact probe systems, requires further investigation.
Laser induced fluorescence spectroscopy of normal and atherosclerotic human aorta using 306–310 nm excitation
Authors: Baraga Joseph J. , Rava Richard P. , Taroni Paola , Kittrell Carter , Fitzmaurice Maryann , Feld Michael S. 
Published: March 2007

AbstractUltraviolet excited laser induced fluorescence (LIF) was studied in normal and atherosclerotic human arterial wall in vitro. Using excitation wavelengths from 306 to 310 nm, two distinct emission bands were observed in the LIF of both normal and pathologic aorta: a short wavelength band, peaking at 340 nm emission, which was attributed to tryptophan; and a long wavelength band, peaking at 380 nm emission, which was assigned to a combination of collagen and elastin. The intensity of the short wavelength band was quite sensitive to the choice of excitation wavelength, while the long wavelength band was not, so that the relative contributions of the bands could be controlled by the precise choice of excitation wavelength. A valley in the spectra at 418 nm was attributed to fluorescence reabsorption by oxy‐hemoglobin.By using 308 nm excitation to observe emission simultaneously from both the short and long wavelength bands, normal and atherosclerotic aorta were spectrally distinct. Two LIF emission intensity ratios were defined to characterize both the relative tryptophan fluorescence content as well as the ratio of elastin to collagen fluorescence in each spectrum. The differences in these two emission ratios among the various histologic tissue types correlated qualitatively with the histologic and biochemical compositions of these tissues. By combining these parameters in a binary classification scheme, normal and atherosclerotic aorta were correctly distinguished in 56 of 60 total cases. Furthermore, atherosclerotic plaques, atheromatous plaques, and exposed calcifications could be classified individually with sensitivitieslpredictive values of 90%/90%, 100%/75%, and 82%/82%, respectively.
Lateral thermal damage along pulsed laser incisions
Authors: Zweig Adrian D. , Meierhofer Brigitte , Müller Otfried M. , Mischler Charlotte , Romano Valerio , Frenz Martin , Weber Heinz P. 
Published: March 2007

AbstractThe damage adjacent to incisions created in dorsal mouse skin by overlapping Er3+ and CO2 laser pulses of a duration of 250 μs is investigated histologically. It is compared to injuries induced by long‐term heating. We demonstrate how the lateral thermal damage near the laser cuts can be explained by heat conduction. We show that it is necessary to introduce as a heat reservoir a layer of tissue that has been liquefied during the cutting process. The width of the thermally damaged region depends mainly on the extension of the liquid material that remains in the cut after the laser‐tissue interaction.
Intraoperative phototherapy (PDT) and surgical resection in a mouse neuroblastoma model
Authors: Davis R. Kim , Smith Lane F. , Thurgood Randy F. , Kereszti Zsolt , Straight Richard C. 
Published: March 2007

AbstractThis study evaluates the effect of intraoperative photodynamic therapy (PDT) using the multiline argon laser (488–514 nm) or the argon‐dye laser (630 nm) combined with surgical resection compared with surgical resection alone in reducing the incidence of C1300 neuroblastoma recurrence in mice. In the control groups, surgical resection alone resulted in 86% ± 12% tumor recurrence. Surgical resection and intraoperative lasing without photosensitizer resulted in 75% ± 27% tumor recurrence with the argon‐dye laser and 55% ± 18% recurrence with the multiline argon laser. In the treatment groups, surgical resection and intraoperative PDT at 630 nm resulted in 56% ± 19% tumor recurrence whereas surgical resection and intraoperative PDT at 488–514 nm resulted in 21% ± 7% tumor recurrence. The cause for the decrease in local recurrence in the control group using the multiline argon laser is unknown, but could it be due in part to hyperthermic effects. Intraoperative PDT was an effective adjunct to surgical resection in preventing local recurrence in this tumor model.
Laser‐Induced hyperthermia in the treatment of liver tumors
Authors: Hahl Juha , Haapiainen Reijo , Ovaska Jari , Puolakkainen Pauli , Schröder Tom 
Published: March 2007

AbstractSeven patients with malignant liver tumors were treated with Nd:YAG laser induced hyperthermia. The laserthermia was performed during laparotomy using Nd:YAG laser with contact sapphire probes with power settings of 6 W. The contact tip was placed into the middle of the tumor and the temperature in 1.5‐2.0cm from the middle of the tumor was raised and held between 41C and 45C for ten minutes. One fatal complication appeared caused by an air embolism. In the postoperative fine needle biopsies on third and fifth postoperative day the sytologic finding in the tumor was necrosis. However, in 30% of the samples there was also a suspicion of cancer cells. In the computer tomography four weeks after the treatment there were also signs of necrosis. It seems that selective destruction of malignant liver tumors is possible with contact Nd:YAG laser induced hyperthemia.
Acute and chronic effects of bone ablation with a pulsed holmium laser
Authors: Stein Eric , Sedlacek Thomas , Fabian Richard L. , Nishioka Norman S. 
Published: March 2007

AbstractA pulsed holmium laser transmitted through a quartz fiber was used to create osteotomies in the facial bones and sinuses of rabbits. The ablation process was quantified and residual thermal injury was assessed by light microscopy. Adjacent thermal damage was determined to vary between 130 and 220 pm and was independent of radiant exposure and pulse repetition rate. In other studies, large osteotomies were made to examine the biological response and to assess the technical feasibility of using fiber‐delivered laser pulses in an operative setting. The animals tolerated the procedure without obvious problems and postoperative follow‐up revealed a vigorous healing response. Because it can ablate both bone and soft tissue and can be transmitted through readily available, flexible quartz fibers, the holmium laser may prove to be a useful adjunct to endoscopic sinus surgical procedures.
Thermal laser probe angioplasty: Influence of constant tip temperature, plaque composition, and probe/vessei diameter ratio
Authors: Vincent G. Michael , Fox Jolene , Johnson Michael D. , Strickland Richard , Garry Stacey L. , Hammond Elizabeth 
Published: March 2007

AbstractThermal laser angioplasty uses constant laser power, producing widely variable tip temperatures in vivo. Results have been sub‐optimal. We studied the effect of 50–400°C tip temperatures on depth of ablation at 192 sites on plaqued and normal human aorta in vitro, and the angiographic and histologic response in vivo of 300–400°C at probe/vessel ratios of 0.5–1.0, in 40 normal canine femoral artery segments. In vitro, there was a direct relationship between tip temperature and depth of ablation, r = 0.71 (all segments), r = 0.74 for fibrous plaque, but a poor correlation in fatty plaque r = 0.35. In fibrous plaque, there was proportionately more ablation at tip temperatures >300°C, mean depth 0.62 mm, than at 150–300°C, mean 0.37 mm, (P <.001). Ablation was similar in plaqued and normal aorta. In vivo, 300°C, 350°C, and 400°C produced similar effects. At probe/vessel ratios <0.8, only disruption of internal elastic lamina was observed. At ratios ⩾0.8, spasm occurred in 39% (7/18), transmural damage in 28% (5/18), and perforation in one of 18. Ablation is not selective for plaque and is highly variable in fatty plaque. Tip temperatures above 300°C produce greater ablation than at lower temperatures. In clinical applications, probehessel rations ⩽0.7 may be most appropriate, and it appears that thermal remodeling may contribute more to outcome than plaque ablation.
Carbon dioxide gas as a perfusion medium for the sapphire probe in laser ablation of human atheromatous plaques: Comparison study with saline
Authors: Yang Xiaoming , Manninen Hannu , Kankkunen Jussi P. , Ji Hongxiu , Naukkarinen Anita , Suhonen Matti , Soimakallio Seppo 
Published: March 2007

AbstractThe effectiveness of CO, gas as a perfusion medium was compared to that of saline in laser ablation of human atheromatous plaque. In an experimental circulation–occlusion model using flowing whole blood, human cadaveric arterial samples were irradiated by a sapphire probe with the Nd‐YAG laser. The following experiments were performed: (1) lasing without perfusion, (2) lasing with saline perfusion of the probe, and (3) lasing with CO2 perfusion. Different perfusion flow rates of saline and CO2 were used. Results showed that the mean ablation area was 1.6‐fold larger with CO2 than with saline perfusion (P < 0.05, Student's t test). The mean lateral injury at the site adjacent to the ablation crater and at the area directly facing the probe was not significantly different with either perfusion medium. The larger ablation area with CO2 was probably due to the fact that CO2 is a good insulator for maintaining a higher probe temperature and keeps the probe free of blood debris. In conclusion, our results show that CO2 perfusion facilitates more effective laser ablation of atheromatous plaque than saline perfusion by the sapphire probe with the continuous wave Nd‐YAG laser.
Vasovasostomy in dogs using the carbon dioxide milliwatt laser: Part II
Authors: Seidmon E. James , Krisch Evan B. , Baer Harry M. , Phillips Steven J. , Tang Chik‐Kwun , Shea Francis J. 
Published: March 2007

AbstractThis is the second study of a two‐prong investigation conducted to learn two different aspects of vasovasostomy in dog vas defe‐rens by using the carbon dioxide milliwatt laser. This investigation involves the evaluation of patency and analysis of sperm.Six dogs underwent vasectomy, followed by vasovasostomies performed between 4 and 12 weeks later, utilizing two approximating sutures and welding with the carbon dioxide milliwatt laser. Metal clips were used both for x‐ray analysis and localization of the vasovasostomy site.All dogs had pre‐vasectomy semen analysis. Following vasectomy each dog underwent ejaculation until azoospermia was obtained. Vasovasostomy was performed and semen was examined. Prior to harvesting, vasography was also obtained. All ejaculates had active sperm noted and 12 of 12 vasograms (100%) revealed patency. The dogs were sacrificed at 4 weeks, 6 weeks, and 8 weeks post‐vasovasostomy. The vasovasostomy specimens were studied with electron microscopy and by histological evaluation.The vasovasostomy was completed in under 90 minutes by using this laser‐assisted technique. This procedure offers to the urologist a more simplified and reproducible operation that can be performed easily and with a potential decrease in hospital costs.
Application of pulsed and continuous wave 1.32 and 1.06 μm wavelengths of the Nd:YAG laser in the canine tracheobronchial tree: A comparative study
Authors: Rebeiz Elie E. , Aretz H. Thomas , Shapshay Stanley M. , Pankratov Michail M. 
Published: March 2007

AbstractPrevious investigations have shown good clinical potential for the use of the 1.32 μm wavelength Nd:YAG laser because its soft tissue absorption is better than that of the 1.06 μm wavelength NdYAG laser. The 1.32 μm wavelength Nd:YAG laser has an absorption coefficient in water that is 10 times higher than the 1.06 μm wavelength Nd:YAG laser. A comparative in vivo study of laser soft tissue effects was performed by using the 1.32 μm wavelength and the 1.06 μm wavelength Nd:YAG lasers in a pulsed wave (PW) mode and continuous wave (CW) mode using a noncontact endoscopic delivery system. A standard 5 mm mucosal lesion was made in the canine tracheobronchial tree down to the level of the perichondrium. Soft tissue and cartilage effects were examined by light and scanning electron microscopy, acutely, 1 week and 2 weeks after operation, and a comparison was made between the different laser modalities. To create similar lesions, higher energy was required when using the 1.06 μm wavelength Nd:YAG laser. Soft tissue injury was greater with the 1.06 μm wavelength in CW mode, and no cartilage damage occurred in the PW mode. Soft tissue and cartilage repair after 1 and 2 weeks was better with the 1.32 μm wavelength laser. In comparison, the CO2laser and the contact Nd:YAG laser proved to be more precise cutting tools than the 1.32 μm wavelength or the 1.06 μm wavelength Nd:YAG lasers. Both Nd:Yag laser wavelengths were useful for coagulation and vaporization of tissues and blood vessels. More studies are needed to determine the effect of the new 1.32 μm wavelengths on endotracheal tumors.
Preliminary experience with the pulsed dye laser for treatment of urolithiasis
Authors: Loughlin Kevin R. , Sharpe John F. 
Published: March 2007

AbstractWe report our initial experience using the pulsed dye laser in 26 patients with urolithiasis. The patients ranged in age from 27 to 82 years; 11 patients were female and 15 were male. Of the 26 patients, 4 stones were in the kidney, 21 were in the ureter, and one was in the bladder. Surgical time ranged from 32 to 130 minutes. All patients were treated under spinal or general anesthesia. The size of ureteral stones ranged from 0.2 to 1.5 cm, and the renal stones 3.0 to 4.0 cm. Chemical analysis of the stones was not available on all patients, but when available, chemical analysis revealed the stones to be calcium monohydrate, calcium dihydrate, or struvite. The use of the Candela miniscope in 11 patients permitted access without ureteral dilation. In 19 patients, ureteral stents were placed. One patient suffered a ureteral perforation. Success was defined as adequate disintegration of the stone for passage of the fragments without the necessity of a secondary procedure. Using this criterion, 22 of 26 patients were successfully treated for an overall success rate of 85%.
Noncontact tissue ablation by Holmium: YSGG laser pulses in blood
Authors: van Leeuwen Ton G. , van der Veen Maurits J. , Verdaasdonk Rudolf M. , Borst Cornelius 
Published: March 2007

AbstractTo assess the feasibility of intra‐arterial tissue ablation by Holmium:YSGG laser pulses (2.1 μm) in a noncontact mode, the transmission of the laser pulses through saline and blood was measured. The temporal interaction between the 500 μs laser pulse and saline at the fiber tip was investigated with time‐resolved flash photography. The penetration depth in blood and saline depended on the fiber output energy. In blood at 37°C, the penetration depth varied from 1.2 to 2.1 mm for intensities of 3.1 to 12.4 J/mm2 per pulse, respectively, whereas its theoretical value for water is 0.33 mm, which is based on the measured absorption coefficient of 3.0 ± 0.1/mm. The large penetration depth was due to the development of a transparent vapour cavity around the fiber tip. In saline, its maximum length was 4.7 mm. Its maximum width was 2.8 mm. The lifetime of the cavity was 450 μs. In blood, ablation of porcine aorta was feasible at a distance of 3 mm. Large fissures observed in adjacent tissue are likely to be caused by the expansion of the vapour cavity. We conclude that, due to a “Moses effect in the microsecond region,” Holmium: YSGG tissue ablation is possible through at least 2.7 mm of blood.
Effects of CO2 laser beam on cortical bone
Authors: Rayan Ghazi M. , Pitha Jan V. , Edwards Janet S. , Everett Royce B. 
Published: March 2007

AbstractSixteen bone blocks from two freshly amputated legs were used to study the effect of CO2 laser on cortical bone. They were divided into two groups. In Group I, the blocks were treated with CO2 laser using 1 mm spot (focused mode). In Group II, they were treated with CO2 laser using 3 mm spot (defocused mode). Two other variables were investigated: the power and time of exposure. Three histologic zones were observed: a superficial zone with black particle deposits (carbonization), an intermediate zone with fibrillations and enlarged empty lacunae, and a deep zone with normal appearing bone. The bony changes in the first two zones combined were superficial in all specimens and did not exceed 200 microns. Increased energy, a focused beam, and time of exposure were all associated with increased matrix changes. CO2 laser can be applied to cortical bone in vitro with minimal residual thermal damage.
Comparison of three lasers for dental instrument sterilization
Authors: Powell G. Lynn , Whisenant Brian K. 
Published: March 2007

AbstractThe sterilization of dental instruments is an area of great interest and recent concern in the field of dentistry. The purpose of this study was to compare the ability of three lasers (argon, CO2, and NdYAG) to sterilize dental instruments. Endodontic reamers were contaminated with microorganisms, lased at various levels of energy, placed in Trypticase soy broth, incubated, and read for growth or no growth to determine sterility. Results indicated that the argon laser is capable of sterilizing selected dental instruments at the lowest energy level (1 watt for 120 seconds) of the three lasers tested. The other two lasers were able to sterilize the instruments also, but at higher energy levels.Results indicated all three lasers capable of sterilizing selected dental instruments; however, the argon laser was able to do so consistently at the lowest energy level of 1 watt for 120 seconds.
Dye laser photocoagulation through experimentally induced retinal hemorrhage
Authors: Obana Akira , Miki Tokuhiko 
Published: March 2007

AbstractThe histological effects of photocoagulation obtained by using each of 4 wavelengths of the dye laser (577, 590, 610, and 630 nm) on experimentally induced retinal hemorrhage in cat eyes were examined. Energy from 577, 590, and 610 nm laser was directly absorbed by red blood cells in the retinal hemorrhage and destroyed the inner layers of the retina. Red blood cells were not directly coagulated with the use of 630 nm laser, and the retinal pigment epithelial cells (RPE cells) and choroidal melanocytes were coagulated. These results suggest that the use of yellow or orange dye lasers for photocoagulative therapy in a retinal hemorrhage is dangerous, because of the risk for destruction of the inner layers of the retina. A 630 nm dye laser is useful for photocoagulation of a retinal hemorrhage, while the laser energy is unable to reach the RPE cells and the choroid with the use of other wavelengths.
Mechanism of CW Nd:YAG laser recanalization with modified fiber tips: Influence of temperature and axial force on tissue penetration in vitro
Authors: Verdaasdonk Rudolf M. , Jansen E. Duco , Holstege Frank C. , Borst Cornelius 
Published: March 2007

AbstractModified fiber tips are used for laser angioplasty of totally occluded peripheral arteries. It has not been established, however, to what extent the mechanism of action of various laser probes is optical, thermal, or mechanical. We examined transparant contact probes (hemispherical contact probes and ball‐shaped fibers) and metal laser probes, coupled to a continuous‐wave NdYAG laser. By using homogeneous thick porcine fatty tissue samples submerged in blood plasma, tissue penetration was measured in relation to the temperature of the probe and the axial force exerted on the tissue. By using 15 W, 1 s laser pulses, the surface of transparent contact probes had to be first contaminated by carbonized tissue particles to achieve tissue penetration. Penetration increased from 1 to 10 mm per pulse when axial force increased from 20 to 100 g. Metal probes had to be sufficiently insulated from the liquid environment by water vapour entrapped in a denatured protein layer to exceed the threshold temperature of 225°C for tissue penetration. When axial force increased from 20 to 80 g at 10 W continuous exposure, the velocity of tissue penetration increased in the range from 1 to 4 mm/s. Tissue penetration by modified fiber tips is attributed to both remodeling and vaporization of tissue. With transparant contact probes, tissue is heated partly by direct light absorption and partly by a hot probe surface. Axially directed force is necessary to displace lateral non‐ablated tissue and to overcome mechanical resistance. We conclude that mechanical dilation due to axial catherization force (Dotter effect) contributes substantially to tissue penetration by transparent contact probes.