1、附录 A 英文原文 Laser Tissue Welding: Laser Spot Size and Beam Prole Studies Abstract： This paper evaluates the effect of laser spot diameter and beam prole on the shape of the thermal denaturation zone produced during laser tissue welding. 2-cm-long full-thickness incisions were made on the epilated back
2、s of guinea pigs in vivo. India ink was used as an absorber and clamps were used to appose the incision edges. Welding was performed using continuous-wave 1.06- m, Nd:YAG laser radiation scanned over the incisions to produce 100-ms pulses. Laser spot diameters of 1, 2, 4, and 6 mm were studied, with
3、 powers of 1, 4, 16, and 36 W, respectively. The irradiance remained constant at 127 2cmW Monte Carlo simulations were also conducted to examine .the effect of laser spot size and beam prole on the distribution of photons absorbed in the tissue. The laser spot diameter was varied from 1 to 6 mm. Gau
4、ssian, at-top, dual Gaussian, and dual at-top beam proles were studied. The experimental results showed that 1-, 2-, 4-, and 6-mm-diameter spots produced thermal denaturation to an average depth of 570, 970, 1470, and 1900 m, respectively. Monte Carlo simulations demonstrated that the most uniform d
5、istribution of photon absorption is achieved using large diameter dual at-top beams. Index Terms Denaturation, laser biomedical applications, laser materials-processing applications, laser welding, Monte Carlo methods, optical propagation. MATERIALS AND METHODS A. Experiments In vivo welding of skin
6、 incisions was performed at constant irradiance to investigate the effect of various laser spot sizes (1-, 2-, 4-, and 6-mm-diameter FWHM) on the extent of thermal denaturation at the weld site. Adult female albino guinea pigs (Hartley, age 78 weeks, weight 400500 grams) were shaved then epilated wi
7、th a chemical depilator (Nair,Carter-Wallace, Inc., New York, NY). Each guinea pig was anesthetized with atropine (0.05 mg/kg), ketamine (30 mg/kg), and xylazine (2 mg/kg) administered by intraperitoneal injection. 1% lidocaine with 1:100000 epinephrine was used as a local anesthetic at each incisio
8、n site. 2-cm-long, fullthickness incisions were made parallel to the spine with a no.15 scalpel. Four incisions were made on the back of each guinea pig. Approximately 25 l of India ink (black India Rapidograph ink, 3080-F, 100-nm particle diameter, Koh-INoor, Bloomsbury, NJ) were applied to the wou
9、nd edges with a micropipette. The animal was then placed prone on a translation stage, in preparation for surgery. Clamps were used to temporarily appose the incision edges during welding. Welding was performed with a continuous-wave (CW), Nd:YAG laser (Lee Laser, Model 703T) emitting 1.06 m radiati
10、on that was coupled into a 600 m -core diameter optical ber (Thor Labs, Newton, NJ). A stepper-motor-driven translation stage (Newport, Irvine, CA) scanned the laser beam along the axis of the weld site at speeds that effectively produced 100-ms-long pulses. Seventy scans were made along each weld；
11、the beam stopped at the end of the weld site for 10 s after each scan. To minimize thermal damage to the skin beyond the weld area, high-reecting metal plates placed on each end of the incision blocked the beam. Experiments were performed at constant irradiance (127 2cmw ) comparing laser spot diame
12、ters of 1, 2, 4, and 6 mm full-width at full-maximum(FWHM), with laser output powers of 1, 4, 16, and 36 W, respectively. The beam prole, as measured by scanning a 200- m-diameter pin hole across the beam, was approximately Gaussian for all spot diameters. The power delivered to the tissue was measu
13、red before each weld with a power meter (Molectron PowerMax 5100, Portland, OR). It shows the experimental conguration used for dye-assisted laser skin welding and summarizes the laser parameters for this study. After welding, the anesthetized guinea pig was euthanized with an intracardiac overdose
14、of sodium pentobarbitol (Nembutal, Abbott Laboratories, North Chicago, IL). The dorsal skin, including epidermis and dermis, was excised with a scalpel and then sectioned. Samples were processed using standard histological techniques, including storage in 10% formalin, processing with graded alcohol
15、s and xylenes, paran embedding, sectioning, and hemotoxylin and eosin staining. A minimum of seven samples was processed for each laser spot diameter and beam prole. The 6-mm-diameter spot study was discontinued after grossly obvious burns developed at the wound site. Thermal denaturation measuremen
16、ts were made using a transmission light microscope (Nikon, Japan) t with crossed linear polarizers (Prinz, Japan). Thermal denaturation was measured laterally from the center of the weld site at three different depths: the papillary dermis, mid-dermis, and base of the dermis. The depth to which one
17、observed denaturation was recorded and divided by the skin thickness to obtain the fraction of a full-thickness weld that was achieved. Measurements were made consistently to the point at which complete thermal denaturation of the tissue was observed. Statistical analyzes were conducted on the histo
18、logical data. ANOVA was used to determine statistical signicance of thermal denaturation measurements between laser spot size groups. B. Monte Carlo Simulation Monte Carlo simulations were run to investigate the effect of various spot sizes (16-mm diameters) and beam proles (Gaussian versus at-top a
19、nd single versus dual beam) on the distribution of absorbed radiation. All simulations were run using code available over the public domain . Several changes were made in the Monte Carlo code to adapt it for use with the geometry of this application. First, because the vertical ink layer in the tiss
20、ue disrupted the cylindrical symmetry assumed in the Original program, the data were stored in Cartesian rather than cylindrical coordinates and a convolution program was not used to generate the laser beam prole. The beam prole was, instead, created using a random number generator ； a large number of photons was used to create the desired beam prole. Second, the vertical ink layer was modeled
