Laser tissue welding: Laser spot size and beam profile studies

This paper evaluates the effect of laser spot diameter and beam profile on the shape of the thermal denaturation zone produced during laser tissue wel ding, 2-cm-long full-thickness incisions were made on the epilated backs of guinea pigs in vivo. India ink was used as an absorber and clamps were use d to appose the incision edges. Welding was performed using continuous-wave 1.06-mu m, Nd:YAG laser radiation scanned over the incisions to produce si milar to 100-ms pulses. Laser spot diameters of 1, 2, 4, and 6 mm were stud ied, With powers of 1, 4, 16, and 36 W, respectively. The irradiance remain ed constant at 127 W/cm(2). Monte Carlo simulations were also conducted to examine the effect of laser spot size and beam profile on the distribution of photons absorbed in the tissue, The laser spot diameter was varied from 1 to 6 mm, Gaussian, Bat-top, dual Gaussian, and dual flat-top beam profile s were studied. The experimental results showed that 1-, 2-,4-, and 6-mm-di ameter spots produced thermal denaturation to an average depth of 570, 970, 1470, and 1900 mu m, respectively. Monte Carlo simulations demonstrated th at the most uniform distribution of photon absorption is achieved using lar ge diameter dual hat-top beams.