#2-1. Body Sculpting Using High Intensity Focused Ultrasound(HIFU)

Various energy-based devices and technology are used for noninvasive subcutaneous fat reduction. Liposonix (Solta) was released in 2011 as a high intensity focused ultrasound (HIFU) device for body sculpting and skin tightening. Liposonix obtained FDA approval for use in abdomen fat and waistline reduction.

HIFU uses the principles that focusing sufficient energy into a small area generates heat and that irreversible adipocyte apoptosis occurs within one second of exposure to temperatures of 56℃ or higher. HIFU is currently approved by MFDS for use in the abdominal and flank fat reduction.

Liposonix uses sound waves and not laser or light energy. Sound waves induce partial pressure change in the medium (air) with consistent vibration and reach the ear drum with longitudinal waves. Sound waves with frequencies beyond 20kHz, the audible range, are called ultrasound. Ultrasound is widely used as a diagnostic tool, as it does not cause tissues damage. Ultrasound has different transmissions depending on the frequency, which means that energy loss and delivery depth can vary based on the frequency. At a high frequency, loss is greater and the transmission depth is shallow, whereas, at a low frequency, the energy loss is small and transmission depth greater. Liposonix uses a frequency of 2MHz,1,000 times stronger than diagnostic ultrasound. Using a transducer specially designed for sufficient subcutaneous delivery and transmission depth, Liposonix converts ultrasound energy into HIFU which is delivered to a small area to generate heat.

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Liposonix focuses ultrasound energy 1.3cm below the skin surface to generate heat (Figure 1). Focused ultrasound energy automatically aims and forms a continuous line at the target depth through advanced pattern delivery system (Figure 2). Sufficient energy, fluence of 140~180J/cm², should be irradiated to bring satisfactory loss of adipocytes. Adipocyte debris are migrated to the liver to be used as an energy source or destroyed. Some are excreted in urine or perspiration. Through subcutaneous inflammation and wound healing, collagenesis takes place, resulting in improved elasticity. This process takes place gradually over 6-12 months.