The aim of this study is to establish device control parameters in creating thermally-induced microscopic lesions in skin, using radio frequency energy. With time, skin ages causing wrinkles and decrease in smoothness. Creating thermal lesions in the skin triggers a natural healing process during which the skin regenerates and improves its appearance. Optical techniques to create lesions are commercially available, however electrical techniques potentially have significant advantages. Primarily, due to the absence of optics, electrical devices are expected to be cheaper to produce. In this thesis the main parameters determining the effect of a radio frequency pulse are established using a skin-mimicking phantom and ex-vivo human skin. The main parameters determining whether or not a lesion is created, and what size and shape it has, are found to be: voltage, pulse length, electrode geometry, skin-electrode interface and impedance. Furthermore, a strong correlation between increase in skin-impedance during a pulse and the creation of a lesion is established. For a given geometry and skin-electrode interface the relation between voltage, pulse length, lesion size and shape is presented. This data allows for an estimation of what kind of lesion is created before applying a pulse. However, variance in results suggests a feedback system is needed to reach high efficacy. Two feedback systems are presented. Firstly it is shown that a parameter (R) containing voltage, impedance, thermal relaxation time and pulse length predicts the probability of creating a lesion. Before applying a pulse the impedance can be measured, and the voltage and pulse length can be adjusted to ensure an acceptable probability of creating a lesion. Secondly it is shown that real-time monitoring of impedance during a pulse allows to predict whether a lesion is created or not. Three impedance signatures are presented, each correlated to a different effect in the skin. Responding to such a signature, by changing the voltage or pulse length, ensures a treatment to have the desired effect.
|Date of Award||30 Apr 2014|
|Supervisor||G.J.H. Brussaard (Coach)|