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
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
