INTRODUCTION
The transcutaneous application of RF energy is a well-established treatment for tissue contracture.1-7 As the electric current permeates a tissue layer, impedance creates heat. This localized thermogenesis is calculable using the Specific Absorption Rate (SAR) equation (Figure 1) assessing local electrical conductivity and magnitude of local electric current density generated around the electrode; the electric field strengths generated is capable of heating tissue in close proximity to the electrode, creating a specific pattern of localized thermogenesis that can be controlled to keep the radius of effect close to the electrode, as shown in Figure 2, promoting predictable and specific heating of target tissue. Thermogenic stimulation of collagen remodeling is the desired outcome,8-9 optimized within a well-defined temperature range, suggesting the need for monitoring and feedback mechanisms that maximize the ability to achieve and maintain therapeutically expedient temperatures within that range while minimizing potential for unwanted tissue injury.
Tissue temperature is regulated by controlling power (the voltage delivered to the electrode) adjusted to compensate for tissue impedance. Integrated thermocouples can provide automatic feedback-controlled power modulation to achieve and maintain therapeutically relevant tissue temperatures subcutaneously.
Additionally, a thermal infrared camera offers real-time monitoring of surface skin temperature. The end result is a device for selective subcutaneous thermogenesis for a variety of potential aesthetic dermatological applications, using real-time feedback mechanisms to safely optimize therapeutic energy delivery.10
In 2008 a trial by del Pino et al.11 evaluated the effect of controlled volumetric RF heating for cellulite of the buttocks and thighs in 26 healthy women (age range, 18 to 50 years) with visible bilateral cellulite. Patients received two sessions of unipolar RF therapy with cooling to maximize patient comfort, at an interval of 15 days. Clinical improvement was evaluated via pre- and post-treatment measurement of the distance between the stratum corneum to the Camper’s fascia and from the stratum corneum to the muscle, with additional evaluation of the structure and change shown in the thickening and realignment of the septae. Contraction and improvement in the appearance of cellulite was reportedly demonstrated. A study by Van der Lugt and colleagues in 200912 investigated the use of transcutaneous RF for treating cellulite with a frequency of 0.6 MHz to 2.4 MHz administered in twelve weekly sessions, 12 minutes on each buttock, with a thermal endpoint of 42°C as measured on the skin. Improvement in cellulite was reported, with high patient satisfaction.
