title: Controlled volumetric heating of subcutaneous adipose tissue using a novel radiofrequency technology.
abstract: 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.
  
  
  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.
authors.affiliation: Cutera Inc., Brisbane, CA 94005, USA. wfranco@cutera.com
authors.forename: Walfre
authors.initials: W
authors.lastname: Franco
authors.forename: Amogh
authors.initials: A
authors.lastname: Kothare
authors.forename: David J
authors.initials: DJ
authors.lastname: Goldberg
mesh_terms: D000818:Animals; D004560:Electricity; D005240:Feasibility Studies; D006358:Hot Temperature; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D008954:Models, Biological; D012867:Skin / Q000528:radiation effects*; D050151:Subcutaneous Fat / Q000528:radiation effects*; D013552:Swine