2.1.3 Automate feedback control loops

There are a number of high-tech sensors built into the BodyTite® hand pieces that communicate with the software algorithm on the workstation (Figure 4).

#### Figure 4.

The GUI screen o the BodyTite® RFAL workstation. On the left hand side, he external (skin) electrode and internal electrode (adipose) cut off temperatures are set by the physician. Increments of 120 s of RF energy are dispended and when the 120 s are up, double clicking on the foot pedal gives another 120 s. On the right-hand side are the real time temperatures of the external skin and internal fat temperatures as measured by the external electrode and internal electrode thermistors. As the user gets within 2°C of the cut off temperature, the audible beep that is emitted when RF energy is on, increases in tempo and when the cut off temperature is reached, either internal or external, the and audible will sound that is characteristic for the external and one for the internal cut-off and the RF energy delivered is terminated to the hand piece and tissue heating stops. When the external and internal temperature is 0.1°C below the cut-off RF energy flow begins again. The automated feedback loop allows heating of the adipose and skin to occur together or independently and not exceed the pre-set amounts.

### BodyTite®: The Science and Art of Radiofrequency Assisted Lipocoagulation (RFAL)… DOI: http://dx.doi.org/10.5772/intechopen.83446

Contact Sensors: within the external electrode there is a contact sensor and if there is loss of contact, the RF flow is cut-off, minimizing the risk of arch burns or excessive flow from the internal electrode. External and Internal Thermistors: there are thermistors in the external electrode and near the tip of the internal electrode (US models only) that continuously measure the local temperature every millisecond. The Thermistors permit the physician to enter the desired cut off temperature of the skin and internal cut off temperature of the adipose tissue and the software algorithm within the workstation will cut off the RF energy when the desired external or internal cut-off temperature is achieved. Temperature Display and Audible Alerts: the device interface displays the internal and external temperatures at all times and has an audible alert when the skin, or internal temperature is within 2°C of the cut-off and, then another distinct audible for the both the skin and internal temperature when the desired cut-off temperature has been reached. When the cut off temperature has been achieved the RF will be turn off and on again around that temperature, allowing the physician to sustain the desired thermal endpoint for a prolonged period of time, if desired.

The treatment time and amount of energy delivered in seconds and KJ is measured.

Impedance Cut offs: impedance is the resistance to RF flow through tissue. As the tissue temperature increases, impedance will decrease and if the impedance drop is too great, then the RF energy will be cut off. Conversely, if the resistance to flow is too great (usual cause is divergent electrodes, where the internal is going one way and the external another), or there is solid tissue between the electrodes, or very fibrous tissue between the two electrodes, the impedance will rise and the RF energy is cut off.

Temperature Surge Protection (TSP): the BodyTite® applicator and workstation will continuously measure the "rate of rise of temperature" and will deliver full RF power if the tissue is being heated at less than, or equal to 20°C/cm<sup>3</sup> /s, but will decrease the RF energy if the rate of rise of temperature is between 20 and 35°C/ cm<sup>3</sup> /s until the rate of rise of temperature is again 20C/cm<sup>3</sup> /s and will turn off the RF energy completely (necessitating stepping on the foot pedal again to start) if the rate of rise exceeds 35°C/cm<sup>3</sup> /s, a process is called TSP, or Temperature Surge Protection, or TSP. This rate of rise of temperature algorithm is empirical and based upon the observations that excellent FSN shortening and soft tissue contraction can be achieved less than 20°, which the risk of thermal injury increases as more tissue is heated/cm<sup>3</sup> /s. The physician does not select an energy setting or desired power when selecting treatment parameters, as the device will automatically give enough RF power to maintain a heating profile of 20°C/cm<sup>3</sup> /s. The US version of the BodyTite® has TSP, while the International version does not and uses high and low internal impedance cut offs rather than TSP. The international version allows the physician to enter the desired power (up to 70 W for the larger BodyTite® hand pieces and 25 W for the smaller FaceTite® applicators and aspirates while it coagulates. as the internal electrode is a hollow cannula and the hand piece can hook up to wall suction. The US version is non-aspirating and all suction is performed after or before the RFAL a non-thermal SAL or PAL cannula.

#### 2.2 Evidence for RFAL thermal contraction

There are a number of well-designed studies that have confirmed significant soft tissue contraction following BodyTite® and RFAL. Kreindel and Mulholland were able to show the vertical, horizontal and oblique fibers of FSN (Figure 5) as the major vehicle for significant three-dimensional soft tissue contraction at the time of surgery [15]. Further, this paper showed that 69° was the optimal temperature for thermal contraction and shortening of the FSN network. Duncan and others [16],

#### Figure 5.

The FSN are shown above connecting the anterior rectus sheet below to the overlying abdominal adipose tissue. The vertical, horizontal and oblique Fibroseptal bands will shorten and contract when the RFAL thermal temperature and stimulation reaches 69°C pulling the overlying soft tissue envelope in tighter association with the underlying muscle and delivering soft tissue contraction.

were able to confirm upwards of 25% soft tissue area contraction after BodyTite® and RFAL at 6 months, which increased to 34% at 12 months. There have been numerous clinical papers outlining the soft tissue contraction advantages of the RFAL applicators in the face, neck, arms, inner thighs and body [17–22].
