Study of Interaction of Laser with Tissue Using Monte Carlo Method for 1064nm Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) Laser

Introduction: Liposuction using laser is now one of the most common cosmetic surgery. This new method has minimized the disadvantages of the conventional liposuction including blood loss, skin laxity and long recovery time. Benefits of the new liposuction methods which include less trauma, bleeding and skin tightening prove the superiority of these methods over the traditional mechanical methods. Interaction of laser with fat tissue has the vital role in the development of these new procedures because this interaction simultaneously results in retraction of skin layers and coagulation of small blood vessels so skin tightening and less bleeding is achieved. Method: Laser lipolysis uses a laser fiber inserted inside a metal cannula of 1 mm delivering the laser radiation directly to the target tissue. Laser lipolysis has a wavelength dependent mechanism, tissue heating and there for thermal effects are achieved through absorption of radiation by the target tissue cells, causing their temperature to rise and their volumes to expand. We used Monte Carlo (MC) method to simulate the photons propagation within the tissue. This method simulates physical variables by random sampling of their probability distribution. We also simulated temperature rise and tissue heating using Comsol Multiphysics software. Conclusion: Because optimum and safe laser lipolysis operation highly depends on optical characteristics of both tissue and laser radiation such as laser fluence, laser power and etc. having physical understanding of these procedures is of vital importance. In this study we aim to evaluate the effects of these important parameters. Results: Findings of our simulation prove that 1064 nm Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) has good penetration depth into fat tissue and can reach inside the deeper layers of fat tissue. We see that this wavelength also resulted in good temperature rise; after irradiation of fat tissue with this wavelength we observed that tissue heated in permitted values (50-65 degrees C), this is why this wavelength is widely used in laser lipolysis operations.