Experimental and numerical assessment of hyperthermic laser lipolysis with 1,064nm Nd:YAG laser on a porcine fatty tissue model

Background and ObjectivesThe aim of this study was to develop experimental and numerical models for a better understanding of hyperthermic laser lipolysis (HHL). Study DesignA 3cm thick porcine fat sample was irradiated over a 4.3x4.7cm(2) area for 2 minutes with a 1,064nm Nd:YAG laser using 1.2W/cm(2) irradiance. Two irradiation scenarios were considered: without and with forced air cooling. Following the irradiation, the sample was left to cool down by natural convection. During the irradiation period, the surface temperature of the sample was continuously recorded by an infrared camera. Additionally, temperature depth profiles during the cooling period were also obtained. A one-dimensional model of the laser irradiation procedure was developed, including light and heat transport. The model was used to determine the absorption coefficient of the fat and the heat convection coefficients from the measured data, and to evaluate the treatment by varying the parameters. ResultsThe measured temperature depth profiles revealed a maximum temperature (45.5 degrees C) at the surface for a non-cooled sample, and a surface temperature of 38 degrees C with a subsurface temperature peak of 42.6 degrees C at a depth of 5.7mm for a cooled sample. This corresponded well with the measured surface temperature increase following the irradiation as a result of heat diffusion from the heated deeper fat layers. The developed numerical model was used to fit the measured data. A good agreement between the model and the measurements was obtained. By varying the treatment parameters, basic empirical relations connecting the treatment, thermal signal, and temperature depth profile parameters were found. ConclusionsThe results of this study provide a better understanding of transcutaneous laser lipolysis. The developed numerical model can be extended to transcutaneous laser lipolysis of human subjects. Lasers Surg. Med. 50:125-136, 2018. (c) 2017 Wiley Periodicals, Inc.