• #2-1. RF and HIFU: Mechanism of Action and Efficacy


    These days, patients are looking for a quick and effective lifting procedure that do not cause downtime. Rapid growth is seen in the field of radiofrequency(RF) and high-intensity focused ultrasound(HIFU) as they may be able to live up to such expectations. In this article, we will look at recently published studies in Korea and abroad that examined the mechanism of action and efficacy of these two increasingly popular modalities. In the next article, I will briefly discuss my clinical experience using RF and HIFU.


    What are RF and HIFU? Monopolar RF has been reported to improve skin elasticity in many studies. It induces a consistent level of heat in the dermis to directly contract collagen and bring immediate skin tightening. The RF energy is electrically generated and is not absorbed by epidermal melanin or scattered. Therefore, significant heat energy is delivered to the dermis while the epidermis is left intact. RF treatment is followed by continuous dermal collagen remodeling and neocollagenesis can be expected for months after treatment.


    Figure 1. Study comparing the efficacy between monopolar RF(Thermage) and HIFU(Ulthera).


    On the other hand, HIFU brings improved skin elasticity and fat reduction1. Its key benefit is that it can deliver thermal energy safely to the lower dermis and SMAS layer(6-7mm from the skin surface). HIFU does not affect the epidermis and allows immediate return to normal activities.



    This Korean study was published in Journal of Cosmetic and Laser Therapy in 2015. In this study, 33 patients aged 27 to 76 years were given monopolar RF(Thermage) or HIFU(Ulthera) treatments for efficacy comparison. MonopolarRF treatment was given using theTC tip(ThermageNXT®) at 2.0-3.5(20-38)J/cm2, a total of 300 shots with 3cm2 tip(3-5passes) and with the frame tip(ThermageCPT) at 2.0-3.5(20-38) J/cm2, a total of 600 shots with total tip(8-10passes). HIFU(Ulthera) treatment was given atthe frequency of 4.4 MHzand focal depth of 4.5mm. Histological examination was carried out before and after treatment for examining histological change. Biopsy specimen was taken from the lateral side of the cheek as 2mm punch and 11samples of monopolar RFTC tip, 11 samples of monopolar RF frame tip, 11samples of HIFU were collected. Collagen and elastin content was evaluated through H&E, Masson’s Trichrome, and Victoria blue staining.


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    It was found that in the upper dermis, monopolar RF led to significant neocollagenesis and neoelastogenesis and HIFU led to significant neocollagenesis and neoelastogenes is deep in reticular dermis.


    -To be continued

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