Think Before You Ink: Modeling Laser Tattoo Removal
Cumnock, Katherine; Gerson, Leigh; Stroncek, Jackie; Yagerman, Sarah
Prior to laser treatment tattoos were removed by destroying the skin containing the ink. The skin would be burned, frozen, or excised surgically. The use of Q-Switched lasers has effectively diminished the abrasive nature of tattoo removal with successful results and is now a commonly used method for tattoo removal. Scientific studies have been conducted that examine the laser intensities and mechanism of removal. These studies have found that the laser selectively heats the thin ink layer beneath the skin, leading to an explosion of the microscopic ink particles. The remnants of these particles, and the cells in which they reside, are subsequently removed by the lymphatic system. The primary aim of this project is to model this laser tattoo removal process. This model uses the heat transfer equation with a laser heat generation term to find the temperature profiles of the ink and surrounding skin layers. Also included in the model are the heat energy effects of evaporation within the tissue as it is heated. A mass transfer equation accounts for the moisture content of the tissue as it is lost to vaporization during heating. Sensitivity analyses performed during the modeling process produced optimal values for the absorptivity of the ink for the Q-Switched Ruby laser, 165m-1. They also determined the optimal value for the absorptivity of the skin, 20 m-1. The developed model was validated with clinical experimental results which claimed that within one 40 nanosecond laser pulse time, the ink particles reached 900 degrees Celsius while the surrounding skin temperature was between 45 and 55 degrees Celsius. Further applications of this model include optimizing laser intensities and pulsation times to reduce the tissue damage and the pain of the procedure.
Laser; Tatoo Removal; Skin Damage