“Radiofrequency” (“RF”) is the term for the portion of the electromagnetic spectrum with frequencies ranging from 3 Hz to 300 GHz as shown in Figure 1 below.
Fig. 1. The Radiofrequency Radiation Spectrum (3 Hz to 300 GHz)
The RF range of 0.468MHz to 40MHz utilized by electrosurgical devices for aesthetic indications including treatment of wrinkles and rhytides, is shown in Figure 2 below. The aesthetic RF range shown in Figure 2 (below) encompasses a very small portion of the entire radio frequency radiation spectrum shown in the yellow area of Figure 1 above.
RF devices are not “new”. In fact, this source of heat has been extensively used in surgery for hemostasis and tissue ablation (electro-surgery) for over fifty years. The traditional use of RF in medical applications was for ablative electrosurgical procedures where the goal was the production of immediate thermal tissue destruction and as a source of energy for dermatologic applications.
Fig. 2. Frequency Spectrum of Predicate Electrosurgical Aesthetic Devices Sold in the United States.
“Electricity”
Radiofrequency encompasses a portion of the electromagnetic spectrum subject to the fundamental properties of matter known as “electricity”. These fundamental properties result from the presence and motion of electrons and protons which manifest as attraction, repulsion, luminosity and heating effects. Each one of us deals with electricity every day, yet very few of us actually know what it is. In a nutshell, electricity is characterized by the flow of electrons through a conductor.
- Atoms: Atoms are the smallest particles An atom is the smallest particle of an element that retains all the properties of that element. Each element has its own kind of atom; i.e., all hydrogen atoms are alike, and they are all different from the atoms of other elements. However, all atoms have certain things in common. Shown below is a nitrogen atom. Nitrogen has seven electrons, seven protons and seven neutrons:
- Nucleus: All atoms have an “inner part”—called the nucleus– composed of tiny particles called protons and neutrons.
- Electrons: Atoms also have an “outer part”. It consists of other tiny particles, called electrons, which “orbit” around the nucleus. Neutrons have no electrical charge, but protons are positively charged. Electrons have a negative charge. The atoms of each element have a definite number of electrons, and they have the same number of protons. An aluminum atom, for example, has thirteen of each. The opposite charges – negative electrons andpositive protons – attract each other and tend to hold electrons in orbit. As long as this arrangement is not changed, an atom is electrically balanced. This is illustrated in the figure below of the aluminum atom, which has :
However, the electrons of some atoms are easily moved out of their orbits. This ability of electrons to move or flow is the basis of current electricity. When electrons leave their orbits, they are referred to as free electrons. If the movement of free electrons is channeled in a given direction, a flow of electrons occurs. As previously stated, the flow of electrons through a conductor characterizes dynamic electricity.
- Conductors: Materials that contain many free electrons and are capable of carrying an electrical current are called conductors. Metals and (generally) water are known as good conductors of electricity.
- Insulators: Materials that contain relatively few free electrons are called insulators. Non-metallic materials such as wood, glass, and rubber are good insulators.
The Use of Electrosurgical Devices for Aesthetic Treatments
In the past decade, RF has been widely applied in the field of aesthetics for the treatment of various indications based on the “skin tightening” which can result from deep RF dermal heating and the resulting collagen “remodeling”. The use of high frequency electrical current in the range of 0.3 to 10 Megahertz (MHz), or radiofrequency (“RF”) current, has been found to produce a highly efficient thermal effect on biological tissue that is dependent on the electrical properties of the tissue. Effective and safe parameters of RF technological characteristics and outputs have been demonstrated by a number of electrosurgical devices for effective aesthetic treatments including the indications of wrinkles and rhytides. The efficiency of high frequency (RF) electrical current for tissue heating has made it useful for electrosurgery and various dermatologic applications. The use of radiofrequency as a modality in the aesthetic treatment of wrinkles and rhytides has been previously established. The mechanism of action is heating and denaturation of dermal collagen with resultant collagen fibril contraction, tissue contraction, and thermally mediated wounding leading to collagen remodeling. Further physiologic responses include increased dermal blood flow secondary to capillary dilatation and thickening of the dermal fibrous band. Temperature ranges within the dermis to achieve these effects have been reported to be 55°C – 65°C, and desirable surface tissue temperature clinical end points reported to be 40- 42° C.