Sprayed areas and heat extraction efficiencies produced by current commercial nozzles may be significantly modified by varying the distance between the nozzle and the sprayed surface.
Frost formation following CSC does not usually affect laser dosage delivered for therapy of subsurface targets. Moreover, frost formation may reduce the risk of cryo-injury associated with prolonged cooling. The epidermal protection during CSC assisted laser dermatologic surgery can be further improved by eliminating the adverse influence of ambient humidity.
An Inverse Monte Carlo program was developed based on a scaleable Monte Carlo algorithm. This program determines the skin optical (.ta and p) properties in vivo using reflectance and thermal measurements as inputs from different skin types, very light to very dark. Some basic assumptions are made: 1) epidermal thickness is close to 100 pni, 2) the scattering in the epidermis is the same or similar to the dermal scattering, 3) the dermal absorption and scattering coefficients are similar between individuals. Experimental measurements of reflectance and temperature were taken. These were input into a pair of Inverse Monte Carlo programs that generated the optical properties for the different skin types. A single layer Inverse Monte Carlo model was employed to determine the optical properties of the dermis. A 2-layer Inverse Monte Carlo program was used to determine the epidermal optical properties.
This study presents a finite element model of a non-ablative RF tissue heating system for dermatological applications. The Thermage® ThermaCool TC™ System consists of a capacitively coupled treatment tip, handpiece, RF generator, and cryogen delivery system.Various electrode geometries were created to generate uniform thermal profiles at specific depths in the tissue. The optimal thermal treatment depth for a clinical indication is influenced by factors such as tissue thickness for a given anatomical location, the desired target for heating in that tissue, and anesthesia factors. Electrodes of ¼, 1, and 1 ½ cm 2 area were evaluated for depth of treatment.A 3D multi-physics finite element model was developed to simulate RF heating in tissue. The program coupled electrical and thermal models to predict the electric field produced and the consequent heating. The electrical portion of the model was verified using an electric field mapping system. The thermal section of the model was confirmed via thermocouple measurements for cooling and infrared imaging measurements for RF heating.The FEM model produced electrical and thermal predictions that were verified with experimental measurements. The finite element model shows significant potential as a predictive R&D tool to assist in RF electrode design and reduce product development time.
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