Online temperature measurement
In selective radiofrequency treatments little has been studied regarding in-depth tissue temperatures. Dr Ludmila Stanislavovna Ellis shares her findings on online temperatures during radiofrequency treatment using the Vanquish from BTL Industries
In the growing aesthetic market, radiofrequency is one of the most popular technological modalities for skin tightening and body shaping treatments. Compared to some other technologies, its main principle has been well studied and is widely known.
The principle of fractional heating in tissue, the mechanism of temperature induced apoptosis in porcine models and the discontinuous temperature measurements have all been published, but there is lack of clinical evidence around in-depth tissue temperature during the therapy.
Without real-time in vivo temperature measurement, some areas might reach temperatures that are too high, whilst other areas might not reach the therapeutically optimal temperatures needed.
One of the main complications in online in-depth temperature measurement is the interference of thermal probes with the source of energy—radiofrequency. The selective radiofrequency device delivers the energy contactless to the fat tissue thanks to its different electromagnetic properties.
The aim of this particular study was to prove selective delivery of energy in vivo and the temperature levels and exposure needed for apoptosis induction.
The study was conducted on two patients who were both males in their early 40s and selected according to specific inclusion and exclusion criteria. Fluorescent optical probes were injected into the abdominal fat area 5 cm right and left away from the umbilicus using a metallic needle.
After correctly positioning the probe and verifying its position was in the proper depth by an ultrasound device, the metallic needle was removed while the probe remained in the tissue. After the probe positioning, each patient was administrated to the therapeutic position and the device applicator was set over the abdominal area. The temperature of the fat layer was continuously measured.
The distance of the skin from the applicator was 1 cm. The therapy power was initially set to 200W and adjusted during the therapy, according to the patient’s feeling. The patients tolerated the therapy well. The average set power was 198W, average delivered energy was 192W and the total therapy duration was 45 minutes.
The surface temperature was captured by infrared thermal imager after the 45 minute protocol based therapy. The therapy surface temperatures were captured by camera over the measured area.
We found that the average temperature after reaching 43C, which is the therapeutic threshold, was 43.7C in the depth of 1cm while in the depth of 2cm the average temperature in the same time was 42.6C. The temperature of 43C was reached in 1cm in 9 mins on patient number 1 and in 16 mins on patient number 2. So on average this was 12.5 min.
This means that the therapeutic range of temperatures was kept in the 1cm fat tissue for the 32.5 mins on average, for the remaining time of the therapy. The temperature difference between the skin surface and in the 1cm depth at the end of the therapy was 3.2 C on patient 1 and 4.2 C on patient 2, making it an average of 3.7 C. The temperature difference between the skin surface and the 2 cm depth at the end of the therapy was 2.9 C on patient 1 and 3.1 C on patient 2 with an average of 3 C.
So while the temperature on the surface stayed relatively low, the temperature of the fat tissue reached higher in both depths measured. Also, in both cases the temperature in the depth of 1cm was higher compared to the 2 cm depth and the skin surface.
The thermal gradient between the skin surface and fat tissue has proven that the thermal focal point is in the depth of about 1cm below the skin surface in the fat tissue. From the measured temperatures and according to the literature we can conclude that the total exposure of the fat tissue in focal depth during the selective radiofrequency treatment is sufficient to influence fat tissue and induce apoptosis.
1. McDaniel D, Weiss R, Weiss M, Mazur C, Griffin C. Two-Treatment Protocol For Skin Laxity Using 90-Watt Dynamic Monopolar Radiofrequency Device With Real-Time Impedance Monitoring. Drugs in Dermatol 2014;13(9):1112-1117
2. Franco W, Kothare A, Ronan SJ, Grekin RC, McCalmont TH. Hyperthermic injury to adipocyte cells by selective heating of subcutaneous fat with a novel radiofrequency device: feasibility studies. Lasers Surg Med 2010; 42(5):361-370.
3. Weiss R, Weiss M, Beasley K, Vrba J, Bernardy J. Operator Independent Focused High Frequency ISM Band for Fat Reduction: Porcine Model. Lasers Surg Med 2013; 45(4):235-239.
4. Elmore S. Apoptosis: A Review of Programmed Cell Death. Toxicol Pathol 2007; 35(4):495-516.
5. Baisch H, Bollmann H, Bornkessel S. Degradation of apoptotic cells and fragments in HL-60 suspension cultures after induction of apoptosis by camptothecin and ethanol. Cell Prolif 1999; 32(5):303-319.
6. Atiyeh BS, Dibo SA. Nonsurgical nonablative treatment of aging skin: Radiofrequency technologies between aggressive marketing and evidence-based efficacy. Aesthetic Plast Surg. 2009; 33,(3)283-94.