May 19, 2020
Ultrasound is used for diagnosing skin disorders1 as well as cosmetic treatment of the skin and subcutis2 and detecting or supporting the management of any complications of cosmetic procedures. For these purposes, there are different types of ultrasound devices that each need trained operators.
Among the cosmetic treatments supported by ultrasound are skin cleansing, facilitating conditioner absorption, skin rejuvenation/tightening, and fat reduction (lipolysis).3 This statement focuses on methods for body contouring and wrinkle reduction with high-intensity focused ultrasound (HIFU) devices that do not involve surgical incisions and therefore exclude technologies such as liposuction even if accompanied by ultrasound-assisted liposuction.4–6 High-intensity focused ultrasound is effective for targeted destruction of adipose tissue to achieve an alteration in the body shape. Micro-focused ultrasound (MFU) is a form of HIFU that targets the dermis and subdermal tissue.7 Micro-focused ultrasound thermally coagulates selective volumes of connective tissue, such as collagen, leading to neocollagenesis and a more robust structural organization.8 High-intensity focused ultrasound and MFU are popular because they do not involve surgical incision.
High-intensity focused ultrasound and MFU induce tissue effects via thermal or mechanical mechanisms. Tissue heating is mainly due to the absorption of ultrasound energy8 and is thought to be a primary mechanism for face and neck skin-subcutaneous tissue tightening with MFU. High-intensity focused ultrasound and MFU aim to selectively heat tissue between 60°C and 70°C. The region of maximal tissue heating with HIFU and MFU is found in an ellipsoidal volume at the focus of the transducer source. As the ultrasound frequency increases, the focal volume decreases (resulting in greater localization), the heating rate increases (due to higher absorption), and the penetration depth decreases (again due to higher absorption).9 Ultrasound-based lipolysis is thought to rely on acoustic cavitation (ie, creation of oscillating bubbles that agitate tissue) to disintegrate fatty tissue. Cavitation may be generated more easily in fatty tissues than other soft tissues.10 Side effects of HIFU and MFU such as pain, tingling, erythema, and edema have been described, albeit mostly temporary.11,12
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2. Mazzoni D, Lin MJ, Dubin DP, et al. Review of non-invasive body contouring devices for fat reduction, skin tightening and muscle definition. Australas J Dermatol 2019; 60:278–283.
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11. Fonseca VM, Campos PS, Certo TF, et al. Efficacy and safety of noninvasive focused ultrasound for treatment of subcutaneous adiposity in healthy women. J Cosmetic Laser Ther 2018; 20:341–350.
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