Facial Skin Tightening With Microfocused Ultrasound and Dermal Fillers: Considerations for Patient Selection and Outcomes

November 2019 | Volume 18 | Issue 11 | Original Article | 1075 | Copyright © November 2019

Gabriela Casabona MD and Kai Kaye PhD

Ocean Clinic, Marbella, Spain 

Abstract
Introduction: Microfocused ultrasound (MFU) is a heat technology that is developed from focused ultrasound (FU) used in a high intense mode to generate heat (HIFU). Patient assessment is very complex and involves more than just addressing complaints. It is a challenge to evaluate, decide on options, and give treatments that guarantee the best outcomes. In order to facilitate the process, the authors divided the protocol into five steps: Assess (expectations, features); Decide (which depth to customize); Select (choose a number of lines to achieve the objective); Plan (combination, if needed); Treat (documentation, safety, and comfort).

Methods: The PubMed search engine was used to search all publications from 1900–2019 that mention HIFU. The information collected was then grouped into the five protocol steps.

Discussion: MFU is a focused ultrasound device that, at certain energy levels, produces heat over 55ºC at the focal point, which leads to thermal coagulation points (TCPs) in the target tissue. The creation of TCPs leads to a healing cascade, ending with neocollagenesis and neoelastogenesis. At different levels, this can bring about either a lifting effect or skin tightening, depending on the structure targeted. Therefore, the two most important tools for precision and efficacy of treatment are visualization with ultrasound and real-time evaluation of severity and structural changes (such as bone or fat loss).

Conclusion: MFU-V is a well-known and, based on the evidence, an effective tool for non-invasive lifting and skin tightening. The secret to successful use of the device is to assess adequately patient needs and expectations and plan ahead for the combination of other treatment if necessary to achieve the desired outcome.

J Drugs Dermatol. 2019;18(11):1075-1082.

BACKGROUND

Microfocused ultrasound (MFU) is a technology developed from focused ultrasound (FU) and used in high intensity mode to generate heat (high intensity focused ultrasound; HIFU). Focused ultrasound was discovered by Frank Fry in 1972 and was used to destroy brain cancer cells.1 HIFU is a modality in which the ultrasound beam is focused precisely on the target to deliver acoustic energy to part of the body in a non-invasive or minimally invasive manner. The purpose of HIFU is to heat a target tissue without affecting the tissue in the ultrasound propagation pathway. HIFU can increase the temperature of a selected area above 55ºC, which results in coagulative necrosis and immediate cell death in a specific depth through a focused ultrasound beam.

Because the ultrasound wavelength at megahertz frequencies has a millimeter-scale beam size and the ultrasound probe has a concave shape, the ultrasound beam can be focused into small, clinically relevant volumes of tissue. The energy absorption raises the temperature at the focus point but increases only to non-cytotoxic levels outside the region.2,3 Almost 30 years later, noninvasive facial treatment with intense microfocused ultrasound (MFU) started to be developed, such as Ulthera® System (Merz North America, Raleigh, NC), which also includes ultrasound visualization (DeepSee®; Merz North America, Raleigh, NC), followed by Doblo (Hironic®, Korea), which does not include real-time visualization in some models, and Ultraformer (Cryomed®, Australia), which does not offer visualization (Table1).

During development, some HIFU parameters were adjusted to reach the goal of generating thermal coagulation zones (TCPs). The final prototype transducer had shorter pulse durations of 50–200ms, a higher frequency of 4 to 7 MHz, and a decreased energy of 0.5 to 10J.4 As a result, more precise energy delivery was achieved with the microfocused ultrasound with visualization (MFU-V) device during aesthetic treatments for facial tissue.

In 2004, the first preclinical trials were started with a prototype device, followed shortly thereafter by several clinical trials.5-8 White and colleagues6 reported the first aesthetic use of focused ultrasonography and its ability to specifically target the