Study of interaction of laser with tissue using monte carlo method for 1064nm neodymium-doped yttrium aluminium garnet [Nd:YAG] laser

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. 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 therefor 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. 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. 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°C], this is why this wavelength is widely used in laser lipolysis operations

Light wavelength dependent circadian and seasonal responses in blackheaded bunting.

Animals in the wild are exposed to daily variations in sun light, viz. duration, intensity and spectrum. Photosensitive blackheaded buntings (Emberiza melanocephala) were exposed to photoperiods differing in the length of light period, wavelengths and intensity. The effects of such light changes were measured on locomotor activity rhythm as well as seasonal responses like development of migratory restlessness: Zugunruhe, body mass and gonadal growth. The results show that the buntings are differentially responsive to light wavelengths and intensities and are indicative of a phase-dependent action of light on the circadian photoperiodic system. These birds seem to use changes in the light variables of the solar environment to regulate their circadian and seasonal responses.

Harmful effects of 41 and 202 MHz radiations on some body parts and tissues.

Many types of invisible electromagnetic waves are produced in our atmosphere. When these radiations penetrate our body, electric fields are induced inside the body, resulting in the absorption of power, which is different for different body parts and also depends on the frequency of radiations. Higher power absorption may result into health problems. In this communication, effects of electromagnetic waves (EMW) of 41 and 202 MHz frequencies transmitted by the TV tower have been studied on skin, muscles, bone and fat of human. Using international standards for safe exposure limits of specific absorption rate (SAR), we have found the safe distance from TV transmission towers for two frequencies. It is suggested that transmission towers should be located away from the thickly populated areas and people should keep away from the transmission towers, as they radiate electromagnetic radiations that are harmful to some parts/tissues of body.