The efficacy and safety of the high‐intensity parallel beam ultrasound device at the depth of 1.5 mm for skin tightening

High‐intensity parallel beam ultrasound (US) is a novel device equipped with Synchronous Ultrasound Parallel Beam (SUPERB) technology applied in anti‐aging treatment. The system is aimed at pathways stimulating neocollagenesis and neoelastinogenesis in the dermis leading to skin tightening and rejuvenation.

rejuvenation that provide effective treatment for skin lifting and wrinkle correction became more popular among patients. 2 Over the last decade, many energy-based devices, including radiofrequency and focused ultrasound (US)-based devices, have been known for competent skin tightening. The tissue tightening mechanism of such procedures is similar; Propagation of heat energy into the dermis layer, leading to partly collagen denaturation, a state that promotes new collagen and elastin production, while the epidermis is preserved. 3,4 Based on the same principle, focused US beam is used to target a restricted tissue area and cause partial denaturation to promote new collagen production, resulting in skin tightening and wrinkle improvement. Focused ultrasonic transducers with varying thicknesses of 4.5, 3, and 1.5 mm have been used to emit US energy directed at various skin layers in order to initiate a biological pathway resulting in skin lifting effect. The 4.5 mm depth transducer is targeted to stimulate superficial musculoaponeurotic system (SMAS) contraction, resulting in collagen remodeling and facelift. 5 Although the results of US devices for skin rejuvenation appear promising, many concerns have been raised, particularly to pain experience and nerve injury due to the emitted energy into the deep skin layer. 6 The 1.5 mm deep mid-dermis layer is targeted for skin laxity treatment due to its high collagen and elastin density. 7,8 However, previous focused US devices left a significant damage at the epidermal layer of the skin. The injury is caused by the 1.5 mm transducer, 4 results in limited energy discharge.
Recently, the high-intensity parallel beam US-based device produced by Sofwave Medical Ltd. was cleared by the FDA for wrinkle improvement, as well as for eyebrow, neck, and submental lifting treatments. This US device uses a Synchronous Ultrasound Parallel Beam (SUPERB™) Technology. It is packed with 1.5 mm depth transducer, producing high amount of energy of up to 5 J. By including a cooling system, it is able to prevent thermal damage to the epidermis ( Figure 1). Therefore, we proposed a study to determine the efficacy of a new generation device, utilizing non-focused high-intensity US parallel beam for skin tightening.

| Overview
The study is aimed to evaluate the efficacy and safety of the highintensity, non-focused US parallel beam device at the depth of 1.5 mm for skin tightening treatment.
The study was conducted in accordance with the Declaration of Helsinki. Thirty-six subjects, 3 male and 33 female, aged 30-80 years with a range of Fitzpatrick skin type II-IV and mild to moderate skin laxity were enrolled in the study. Subjects were enrolled from October 2021 to April 2022 on a first come, first serve basis.
All participants were informed about the study protocol. A signed informed consent was obtained from each participant before joining the study. Digital photographs and three-dimensional photographs were taken with Antera 3D camera (Antera Pro® v2.8.5; Miravex Limited) at baseline, 1 and 3 months post-treatment ( Figure 3) in order to assess the efficacy of the high-intensity US parallel beam device for skin tightening. Antera 3D™ software was used to analyze the images. Pain was evaluated by pain measurement scale, immediately after treatment. Any adverse events (AEs) reported by the participants throughout the study period and/or observed by the study staff were documented and examined by a dermatologist.

| Study plan
The planned time frame of the study was 4 months in total and con-

| Inclusion and exclusion criteria
Inclusion criteria were healthy males and females aged 30-80 years old, diagnosed with mild to moderate sagging skin at the face and neck areas and opted for a skin tightening procedure. Subjects were excluded if they had local infections; active skin diseases that might affect wound healing; previous surgical face lifting; previous ablative or non-ablative skin procedures within 6 months prior to the study; botulinum toxin or filler within 6 months before the study.

| Treatment
The treated area was cleansed by a regular facial cleanser and allowed to dry completely. All make-up and lotions were removed completely. Upon patient's request, topical anesthetic cream (7%, lidocaine-prilocaine) was applied to the treatment area for 45 min. Ultrasonic gel was applied to the treated area and served as a coupling medium.
The non-focused US parallel beam transducers discharged  (Table 1).
After treatment, the area was cleaned and the ultrasonic gel was wiped-off. The subjects were informed that small bumps may develop on their face within 24 h and expected to heal up spontaneously. All participants were instructed to notify the clinic if any side effect occurs after the procedure for further dermatological examination. Afterwards, they were resumed to normal life activities with no restrictions.
Continuous variables were reported as mean ± standard deviation (SD). The mean volume difference and 95% confidence interval (CI) were also reported.

| RE SULTS
Thirty-six Thai participants, 3 male and 33 female (mean age 55.14 ± 10.11), with Fitzpatrick skin type II-IV and mild to moderate skin laxity were recruited in the study. Twenty-four patients completed the trial and arrived to both 1-and 3-month follow-up visits.
Thirty-one participants and 29 participants arrived to follow-up at 1 and 3 months, respectively.
The obtained images were analyzed quantitatively by Antera 3D® camera systems (Figure 2). The mean depression volume (MDV) and its SD were calculated and represented in percentages, relatively to baseline (100%) (Table 2, Figure 3). It was found that the MDV percentage change from baseline to 1 and 3 months post-treatment is statistically significant for all four treated areas ( Table 2). The biggest MDV percentage change was after 3 months for right and left MLs with a decrease of 15.68% (right) and 15.92% (left) compared to a decrease of 9.58% and 13.92%, respectively, after 1 month post-treatment (Table 2, Figure 3). The other two areas showed a statistically significant MDV change as well. For the right NLFs, the measured MDV change was 11.85% 1 month posttreatment and 12.54% 3 months post-treatment. For the left NLFs, the volumes were 9.97% and 11.2% 1 and 3 months post-treatment, respectively (Table 2, Figure 3). However, upon examination of MDV change from 1 to 3 months, no significant MDV change could be observed (Table 2).
An improvement pattern could be observed in right NLF and left ML as early as 1 month post-treatment in 75% of the subjects.

| Safety and adverse effects
All participants were able to tolerate the procedure without topical anesthesia. Average pain score was 6.64 ± 1.20 on 0-10 scale (while 0 represents no pain at all and 10 represents severest pain). No AEs were reported. No adverse effects were observed or reported during the entire study course. All participants could resume their activities after the treatment with no downtime. Changing in skin sensation, burning, swelling, and nerve injury were not recorded in our trial.

| DISCUSS ION
The aim of this study was to examine the possible implementation of the new high-intensity US parallel beam US device at the depth of 1.5 mm, for skin tightening treatment.
As a predicate device, Ulthera® is a microfocused ultrasound device (MFU) that has been used for non-invasive skin lifting since 2009. 9 Ulthera was cleared by the FDA for eyebrow, neck, and submental lifting. 9   In conclusion, the high-intensity parallel beam US device at the depth of 1.5 mm was proven to be clinically safe and effective for skin tightening, particular in lower face area. This novel technology could be an option for patients seeking for non-invasive skin tightening and rejuvenation with promising results and no downtime.

ACK N OWLED G M ENTS
The authors thank Oleg Bedich for English correction of the manuscript. The authors are grateful for Dr. Michael H. Gold for reviewing statistic analysis and manuscript.

FU N D I N G I N FO R M ATI O N
No financial support was received in this study.

CO N FLI C T O F I NTE R E S T S TATE M E NT
The authors declare no conflicts of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author upon reasonable request.

E TH I C S S TATEM ENT
The study was conducted in accordance with the Declaration of Helsinki. Written and informed consent was obtained from all the participants of the study.