The increase in laparoscopic surgery has resulted in an increased need for a safe and reliable method of obtaining minimally invasive operative hemostasis. Because the traditional "open" methods of controlling bleeding (pressure, tying, and suture (¡gating) are not as easily applied in the laparoscopic arena, a heavy reliance on forms of tissue and vessel coagulation is necessary. To better assess these forms, we compare monopolar, bipolar, and ultrasound energy, in addition to laser energy used in a novel application. In the first part, 20 rabbit mesenteric arteries that measured 1 to 1.5 mm in diameter were coagulated using each of the technologies. We measured the time to coagulation, the efficacy of hemostasis, lateral tissue damage, and local tissue temperature of the vessels when exposed. Part 2 consisted of a survival study using 12 New Zealand white rabbits. In each of these two groups splenectomies were performed. A laser-heated forceps was compared to a monopolar electrosurgery device for the speed of the operation, blood loss, and adhesion grade at necrosectomy. In addition, the speed to cauterization of the iliac vessels and the amount of tissue damage was measured. These vessels were also examined for the extent of microscopic damage. Bipolar electrosurgery was much slower than the other modalities, while monopolar electrosurgery caused significantly more tissue damage and elevation in lateral tissue temperature. The ultrasound technology and the laser-heated forceps were equally safe and efficacious instruments. There was no significant difference in the ability of the laser-heated forceps or the monopolar cautery to perform the splenectomy safely. However, the forceps cauterized the iliac vessels faster and with less lateral thermal injury than the ultrasound device. Although each instrument has its place in the surgical armamentarium, the ultrasound technology appears to be the safest and most efficacious commercially available device for obtaining hemostasis. The laser, as it is applied in this setting, was also highly effective, but still a prototype device.Address reprint requests to:
A coherent phase-locked laser array has been experimentally demonstrated by combining the outputs of seven individual fiber lasers together in a self-Fourier cavity. By analyzing the interference fringes of the laser output in the far field of the array, a fringe visibility was measured of V=0.87, indicating a coherence of 0.73. The total output power of this laser array when operated as a coherent ensemble was 0.4watts.
Four-@rave-mixing techniques mere used to establish and probe refractive-index gratings in Eu'+doped silicate and phosphate glasses. Vixen the Eu'+ ions are resonantly excited, superimposed transient and permanent gratings are formed. The former are characteristic of population gratings of excited Eu'+ ions while the latter are attributed to local structural modifications of the glass hosts. The time dependences of the grating buildup, decay, and erasure are reported as a function of temperature, laser power, and "verite"'-beam crossing angle for each of the samples. The results suggest the use of laser-induced gratings in these glasses in applications such as amplitude-modulated phase-conjugate reflectors.
We have investigated the fragmentation of gallstones using the pulsed Ho:YAG laser, comparing it to lithotripsy using the visible pulsed-dye laser. We find that the physical mechanisms of stone fragmentation appear to be quite different in the two cases. Using high-speed photography, measurement of acoustic transients, time-resolved optical emission spectroscopy, and direct microscopic observation, we have analyzed the interaction of the Ho:YAG laser with both water and gallstones. We propose a new model in which fragmentation begins with absorption of the laser light by the stone surface. This is followed by melting and ejection of stone material, which is then swept away by the vapor bubble formed by the absorption of the Ho:YAG laser light by water. This model is in excellent agreement with our experimental observations, and differs substantially from the model developed by Teng et al. for laser lithotripsy using the visible pulsed-dye laser.
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