The Study for Arthroscopic Laser Meniscotomy: Selection of The Proper Laser for Arthroscopic Laser Meniscotomy
Masato NakagawaAkira FujikawaTsunenori AraiMakoto KikuchiShiro MurakoshiKatsuya NakagawaMinori HashimotoYukio UedaMinoru Shidara
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Abstract:
To select a proper laser for arthroscopic laser meniscotomy, we studied the menisci ablation rate and damaged layer thickness made by various laser irradiations. The pig knee-joint menisci were used as sample materials. We use eight different lasers from UV region to IR region, pulsed or cw: ArF, KrF, XeCl, XeF excimer lasers, Ar+ UV, Ar+ visible, CO and CO2 lasers. We irradiated these lasers on menisci at an input power density of 60J/cm2/sec.The proper laser for the arthroscopic laser meniscotomy must indicate high ablation rate and thin damaged layer for menisci. Furthermore it can be delivered by flexible fibers. In this point of view, we concluded that the proper laser satisfying those requirements may be XeC1 excimer laser.Keywords:
Laser Ablation
Excimer
Without additional fluorine donor, the Kr/Ne mixture was excited in a excimer laser with Teflon surface preionization plates. The relative UV spectrum was obtained by ways of spectrograph and scanning. The formation of KrF excimer was affirmed. The temporal characteristic of relevant spectra was analyzed. It was found that the lasting time of the KrF excimer emission is about five times as much as that of the discharge current pulse. This indicates that the main process of forming KrF excimer is harpooning reaction but the ion combined reaction that is the main process in general KrF laser.
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In this paper, experimental study of two kinds of typical excimer lasers (XeCl: 308 nm, 30 ns and ArF: 193 nm,17 ns) etching PC, PI, and PMMA is described. The mechanism of excimer laser etching polymer is mainly discussed, and the performances of the two kinds of excimer lasers etching the polymers are compared.
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Since the suggestions of Gudzenko and Yakovienko,l intensive studies for photo-assisted collisions have been carried out experimentally and theoretically for various collision schemes. Previously, we have reported the formations2 of KrF excimer through photo-assisted collision between Kr and F atoms, and also its applications3 to the kinetics of KrF excimer. In the present paper, we report on a new formation process of KrF excimer induced by 248-nm photon in the laser intensity region higher than the previous works.
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A new formation process of the KrF excimer by irradiating the Kr/F 2 gas mix with KrF laser beam is reported. The formation process is assigned as a laser-induced harpooning reaction through two-photon pumping. This process has made it possible to prepare KrF excimers in highly excited vibrational states under simple and control lable conditions, and has enabled the quantitative investigation of the vibrational relaxation processes of the KrF excimer.
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Vibrational energy relaxation
Two-photon excitation microscopy
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The improvement of lifetime plays important role in application and popularization of excimer lasers.Examplfying the discharge pumped XeCl excimer lasers, the laser charmber and the fast switch which have strong influence on excimer laser lifetime has been discussed.
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To determine the human corneal threshold ablation energy density for the 193-nm ArF excimer laser, approximating clinical conditions.The VISX Star (Santa Clara, CA) 193-nm argon fluoride excimer laser was used to ablate the cornea in human eye bank eyes under clinical conditions. Corneas were exposed to energy densities of 10, 20, 30, 35, 40, 45, and 140 to 160 mJ/cm2. Corneas were fixed for light and transmission electron microscopy immediately after laser exposure.Different ablation thresholds for various corneal structural elements were observed. The ablation threshold for the collagen in the corneal stroma was determined to be 30 mJ/cm2. Keratocytes had ablation thresholds of 40 mJ/cm2. These different ablation thresholds accounted for the production of stromal peaks and valleys, with the keratocytes atop the peaks.Different corneal structural elements have different ablation threshold energy densities.
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Laser Ablation
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Recently, pulse compression of XeCl, KrF, and XeF excimer laser pulses using saturable absorbers has been reported.1 We used a similar technique to shorten pulses of the 222-nm KrCI line from a Lumonics model TE-860-2 excimer laser.
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Pulse compression
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Laser ablation of Al, Ni, Fe, and Cu was investigated for pulse durations of 0.1, 1 and 5 ps at fluences up to 100 J.cm-2. The ablation depth per pulse was measured and the ablation thresholds were estimated. The increase of the pulse duration results in a decrease of the ablation rate. The presence of a molten phase is clearly expressed at fluences above 10 J.cm-2. Molecular Dynamics simulation was used to model the laser ablation process in the case of Fe, Al and Ni.
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Pulse duration
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Measurements were made of the effect of the He addition to XeF and KrF excimer lasers using fluorine-containing fuels. A monotonic decrease of laser output with increasing He was observed. The kinetic arguments of why this would be expected in this and other similar excimer laser systems are presented.
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Fluorine
Gas laser
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