Background and objective: The objective of the present study was to demonstrate the feasibility of varying the size of the heating volume of subcutaneous adipose tissue using a novel radiofrequency (RF) technology that controls the delivered energy distribution on the skin surface.
Study design/materials and methods: Changes in the distribution of the electric potential at the skin surface due to frequency adjustment of a novel RF device were experimentally characterized on human skin at 500 kHz, 1, 2, 3, and 4 MHz. These measurements were used to model RF-induced electric fields and power absorption. Thermal measurements in ex vivo animal models were used to complement the initial mathematical modeling.
Results: At 500 kHz the electric potential on the skin surface was nearly constant across the RF applicator surface. At 4 MHz the electric potential dropped 30% from the center to the edge of the RF applicator. At the centerline of the RF applicator, modeling shows that within a 3 cm subcutaneous fat layer the absorbed power at the bottom layer was 40% less than that at the top for 500 kHz. The absorbed power decreased 80% for 4 MHz. Temperature measurements show uniform heating across a horizontal array of probes with 500 kHz. Temperatures were significantly higher at the center probes for 4 MHz. Cross-sectional radiometric temperature maps show a larger heated tissue cross-section using 500 kHz as opposed to 4 MHz.
Conclusions: As the frequency increases (i) the electric potential at the skin surface decreases from the center to the edge of the RF applicator; (ii) the difference between the power absorbed at the top and bottom of the subcutaneous fat layer increases; (iii) the difference between the power absorbed at the center and the periphery of the exposed subcutaneous fat volume also increases; and, consequently, (iv) the size of the heated subcutaneous fat volume decreases. Such a device when used in humans may allow for differential delivery of heat to varying fat thicknesses and anatomic areas.
Copyright 2009 Wiley-Liss, Inc.