The history of body contouring started with fat removal by using curettage in 1921 by Duiarrier [1]. During the past several decades, body contouring by liposculpting has evolved dynamically with the introduction of many innovative methods and devices. Especially, the introduction of tumescent technique, mixing lidocaine and epinephrine in saline solutions, has dramatically evolved liposuction technique by eliminating the need for general anesthesia and hospital admission, and also reducing the risk of bleeding complications.

During the past decades, mechanical liposuctions have been used with many mechanical adjuncts such as ultrasound-assisted liposuction, power-assisted liposuction, vibroliposuction, and laser-assisted liposuction [2]. Proponents of each of these techniques have attempted to demonstrate greater safety and efficacy than traditional liposuction techniques [3].

Laser-assisted liposuction technique was first performed by Apfelberg in the 1990s. YAG optical fiber was used with in the liposuction cannula [3]. The laser energy using optic fiber in direct contact the fat tissue could induce adipocyte lysis by thermal damage [4]. This laser induced thermal damage decreases intraoperative blood loss and postoperative ecchymosis and improves skin tightening [3]. These days, current laser-assisted liposuction is aimed to provide more selective adipose tissue damage by manipulating various wavelengths [5], with theory of selective photothermolysis. The selective photothermolysis could disrupt the membrane of adipocytes and allow the extracellular drainage, and also induce tissue tightening by heating the collagenous fibrous septa and reticular dermis [2].

Various laser systems with multiple wavelengths have been introduced for laser-assisted liposuction. Current technology uses small, 1-2 mm optical fibers inserted through small cannulas to transmit the laser into the subcutaneous tissue [6]. The most representative and popular laser system is 1,064-nm Nd:YAG laser with its good tissue penetration and broad tissue heating. For more selectivity for adipose tissue, laser system with 1,980-nm and 2,300-nm wavelengths has been proposed and proved its efficacy [6]. The goal of this study was to analyze data on the safety and efficacy of dual-wavelength laser-assisted lipolysis on belly circumference.

Study design

Twenty adults who had concerns about their abdominal obesity were recruited into a prospective clinical trial. The overall purpose of this outcomes study was to assess whether the Liposci (WONTECH), dual-wavelength laser-assisted lipolysis, will safely reduce the abdominal circumference after the procedure and reduce the depth of abdominal fat in ultrasound monitoring. The first subject was enrolled on January 7, 2020 and the last on June 5, 2020. Follow-up was completed in August of 2020. Inclusion and exclusion criteria are outlined in Table 1.

Table 1 . Inclusion and exclusion criteria for patient recruitment

Criteria for patient recruitment
Inclusion
Age >18 yr
Body mass index ≤35 kg/m2
Subcutaneous fat thickness measured by caliper ≥2.5 cm
No plan for body contouring procedure during the experiment
No plan for any diet or habit change regarding weight reduction during the experiment
Voluntarily decided to participate and wrote consent
Exclusion
Pregnancy
History of blood clotting disorder
History of aesthetic treatment or procedure at abdomen within 12 mon
History of implantation of pacemaker or defibrillator
Uncontrolled diabetic mellitus or cardiovascular disease
Low-density lipoprotein cholesterol ≥190 mg/dl
Under treatment of hepatitis within 12 mon
Surgical history at abdomen within 18 mon
Cancerous or pre-cancerous lesion at abdomen
Infection, wound, or scar on abdomen including keloid or hypertrophic scar
History of abdominal hernia
History of photosensitivity
History of immunosuppression treatment or autoimmune disease including human immunodeficiency virus
History of neurologic disorder including diabetic neuropathy

On the screening visit, all the candidates were provided informed consent. Medical, surgical, social histories were performed. Vital sings including blood pressure, weight, height, temperature, and body mass index (BMI) were obtained.

Standardized two-dimensional digital photographs were taken to document any further change in the appearance of the abdominal area.

Subject group received abdomen contouring treatment with laser-assisted lipolysis and returned for follow-up visits at 1, 4, and 12 weeks. Abdominal circumference and subcutaneous fat thickness and BMI were evaluated at procedure day and every follow-up visit. Global Aesthetic Improvement Scale (GAIS, in the Table 2) was used to evaluate the satisfaction of procedure at every follow-up visit. Numeric Rating Scale (NRS) scoring system with numbers from 0 to 10 (none to worst) was used to evaluate the pain and discomfort immediately after the procedure.

Table 2 . Global Aesthetic Improvement Scale

Scale
1	Much worse
2	Worse
3	No improvement
4	Improved
5	Much improved

Intervention

Surgical consent was provided, and surgical procedures were performed in the Soonchunhyang University Bucheon Hospital Department of Plastic and Reconstructive Surgery. On the day of procedure, the areas to be treated were marked with the patients in the standing upright position. Intravenous conscious sedation was performed before the procedure. Continuous-pulse oximetry and intermittent blood pressure was monitored during the procedure.

After a standard sterile preparation and surgical drape, 1% lidocaine with epinephrine was injected in the incision sites. After initial puncturing with 18-gauge needle, infiltration cannula was inserted for tumescent infiltration technique. The solution consists of Ringer’s lactate solution containing 0.10% lidocaine, 12 ml of sodium bicarbonate, and 1.5 ml of a 1:1,000 epinephrine concentration. It was injected into the superficial and deep subcutaneous fat layer for 30 minutes and its volumes ranges from 500 ml to 1,000 ml depending on the anatomic region and patients’ BMI.

After infiltration, the 1,980-nm/2,300-nm Liposci dual-wavelength laser at 10 kHz with was used through fiberoptic cables with diameters of 400 µm. The power setting was 1.3 W. The fiberoptic cannula was placed in the superficial and deep subcutaneous fat layer, moving forward and backward at least 1 cm/s. When manipulating the cannula, the surgeon used skin pinching and manual palpation to detect the end-tip of cannula, to avoid thermal injury to skin. Infrared camera (Ti45; Fluke) was also used to monitor the skin temperature under 41°C. Depending on the patient’s fat volume, the procedure was performed for 5 minutes per site, and the total procedure was set so as not to exceed 60 minutes. After the procedure, all incisions were closed with 5-0 nylon, and the patients were placed in compression garments.

Patients were discharged the same day, after total recovery of orientation. Oral analgesics and antibiotics were prescribed for the patients, and all the patients returned to normal daily activities within next day of procedure.

Measurement of abdominal circumference

The circumference of abdomen was measured by clinicians using a tape measure at screening visit and follow-up visits of 1, 4, and 12 weeks. The midpoint between the lowest margin of rib cage and the anterior superior iliac spine was chosen for measurement of abdominal circumference. Participants were asked to hold breath after full exhalation during the measurement. The average value of serial twice measurements was recorded.

Measurement of subcutaneous fat thickness

Ultrasound (Accuvix XQ; Samsung Medison) was used to measure the thickness of abdominal subcutaneous fat tissue of participants by the clinicians at screening visit and follow-up visits of 1, 4, and 12 weeks. The evaluation was performed by measuring the distance between the epidermis and muscle fascia at the specific point of abdomen (3 cm right and 3 cm under the umbilicus). To avoid any fat compression errors, the ultrasound probe was placed above a given site without any pressure by using a thick layer of ultrasound gel between the probe and the skin.

Statistical analysis

The paired t-test was used to compare the data of abdominal circumference, ultrasound-measured subcutaneous fat thickness and patients’ weight between the baseline and of 1, 4, and 12-week follow-up. The results were expressed as the mean ± SEM. Statistical significance was set at p < 0.05.

Participant characteristics

A total 20 patients were enrolled in the research, and they underwent successful laser-assisted lipolysis procedure. Of these, 1 was excluded for loss of follow-up visits. Subject demographics are listed in Table 3. Mean age was 43.60 ± 11.87 (range, 21 to 64 years), and 100 percent were female. None of the patients had previous procedures regarding fat reduction. Severe complications were not reported after the lipolysis procedure, including deep vein thrombosis, major bleeding, or death. Case requiring hospitalization was not reported. Also, there were no burn, hematoma, seroma, or scars regarding the procedure.

Table 3 . Subject demographics

Characteristic	Value (n = 19)
Sex
Female	19
Male	0
Age (yr)
Mean (range)	43.60 (21-64)
Body mass index (kg/m2)
Normal weight (18.5-24.9)	11
Overweight (25.0-29.9)	8

Abdominal circumference

When compared with the baseline, a statistically significant reduction in abdominal circumference was observed at 1-week, 4-week, and 12-week follow-up visits after treatment (all p < 0.05). At 1-week, the average reduction of abdominal circumference was –2.68% (–2.34 ± 2.83 cm). During 12-week evaluations, the abdominal circumference measurements were further reduced ranging from –3.86% (4-week) to –4.23% (12-week). All the presented data were compared with the baseline value (Tables 4, 5).

Table 4 . Summary of Liposci^a) patient body measurement data in 1, 4, and 12-week data

Body measurements	Pre-operative	1-week f/u	p-valueb)	4-week f/u	p-valueb)	12-week f/u	p-valueb)
Abdominal circumference (cm)	85.41 ± 6.99	83.24 ± 6.57	<0.05*	82.16 ± 5.47	<0.05*	81.85 ± 5.84	<0.05*
Subcutaneous fat thickness (cm)	2.98 ± 0.45	2.61 ± 0.49	<0.05*	2.37 ± 0.40	<0.05*	2.28 ± 0.48	<0.05*
Weight (kg)	64.47 ± 7.84	64.49 ± 7.86	0.92	64.28 ± 8.01	0.45	63.97 ± 7.95	0.10

Values are presented as mean ± standard deviation.

^a)Liposci (WONTECH). ^b)Paired t-test for comparing preoperative with 1, 4, and 12-week follow-up (f/u). *Significant difference at p-value ≤0.05.

Table 5 . Changes in abdominal circumference, USG measurement, and weight in 1, 4, and 12-week data

Duration		Baseline		1-week data			4-week data			12-week data
		Mean value		Difference value	Difference rate (%)		Difference value	Difference rate (%)		Difference value	Difference rate (%)
Abdominal circumference (cm)		85.41 ± 6.99		–2.34 ± 2.83	–2.68		–3.42 ± 3.34	–3.86		–3.73 ± 3.86	–4.23
USG measurement (cm)		2.98 ± 0.45		–0.37 ± 0.39	–12.21		–0.61 ± 0.39	–19.91		–0.70 ± 0.29	–23.75
Weight (kg)		64.47 ± 7.84		0.03 ± 1.07	0.06		–0.19 ± 1.07	–0.31		–0.50 ± 1.28	–0.77

Values are presented as mean ± standard deviation.

USG, ultrasonography.

Ultrasound measurements

The thickness of abdominal subcutaneous fat tissue measured by ultrasound was also significantly reduced when compared with the baseline during the serial follow-up visits after procedure (all p < 0.05). At 1-week, the average reduction of abdominal subcutaneous fat thickness was –12.21% (–0.37 ± 0.39 cm). During 12-week follow-up measurements, the fat thickness was further diminished ranging from –19.91% (4-week) to –23.75% (12-week) (Tables 4, 5).

Weight

The average body weight of 1-week showed slightly increasement of 0.06% (0.03 ± 1.07 kg). However, the follow-up measurement of 4-week and 12-week showed statistically significant reduction of body weight when compared with the baseline. The reduction rate was –0.31% (–0.19 ± 1.07 kg) in 4-week measurement and –0.77% (–0.50 ± 1.28 kg) in 12-week measurement. All was statistically significant (p < 0.05; Tables 4, 5).

Digital photographs

The digital photographs showed significant volumetric change in abdomen and flank area with visual aesthetic improvement. It was correlated with the reduction of abdominal circumference and fat thickness measured by ultrasound (Fig. 1).

Figure 1. Significant volumetric change in abdomen and flank area was observed after laser-assisted lipolysis procedure, and this change was correlated with the reduction of abdominal circumference measurement and soft tissue fat thickness, which was measured by ultrasound (Accuvix XQ; Samsung Medison). (A) Digital photograph and ultrasound image before laser-assisted lipolysis procedure. (B) Digital photograph and ultrasound image 12-week after laser-assisted lipolysis procedure.

Patient comfort

The NRS scale which was checked immediately after the procedure showed the average score across all participants totaling 2.47. Most of the patients found the procedures quite comfortable with mild fatigue, and no adverse event was reported during the procedure and 12-week follow-up.

Global Aesthetic Improvement Scale

The GAIS was conducted by both patients and surgeons. In 1-week evaluation, the patients’ GAIS was 4.16 ± 0.60 and the surgeons’ GAIS was 4.00 ± 0.94. In 4-week evaluation, the patients’ GAIS was 4.16 ± 0.37 and the surgeons’ GAIS was 4.26 ± 0.81. The GAIS was lowest in 12-week evaluation in both patient and surgeon group. It was 4.11 ± 0.57 and 3.42 ± 1.17 in each group. The GAIS of surgeon group was lower than the GAIS of patient group in 1-week and 4-week evaluation, but it was not statistically significant. However, in the 12-week evaluation, the surgeons’ GAIS was lower than patients’ GAIS, and it was statistically significant (p < 0.05; Fig. 2).

Figure 2. The Global Aesthetic Improvement Scale (GAIS) of surgeon group was lower than the GAIS of patient group in 1-week and 4-week evaluation, but it was not statistically significant. However, in the 12-week evaluation, the surgeons’ GAIS was lower than patients’ GAIS, and it was statistically significant (p < 0.05).

According to the results of the National Health and Nutrition Survey conducted on adults in 2016, the total amount of time for exercise decreased and the intake of fat increased when comparing to the past. As a result, the number of people who fall under obesity is increasing, and the incidence of obesity-related diseases including hypertension and diabetes is also increasing. Accordingly, as awareness of obesity-related diseases becomes more common, interest in not only slim and healthy body but also fat removal surgery and procedures for treating obesity is also increasing.

Various laser systems with multiple wavelengths have been introduced for laser-assisted liposuction to treat abdominal and truncal obesity. Starting with the first U.S. Food and Drug Administration approved Nd:YAG laser surgery device with a wavelength of 1,064-nm, laser devices with various wavelengths are being developed [7]. Until now, lasers with a wavelength of 1,064-nm have been most widely used, but as the characteristics of absorbing water and fat vary depending on the wavelength, efforts to increase the efficiency of fat melting by using various wavelengths have been continued.

As the wavelength increases, the absorption rate of fat and water also increases. Within the wavelength range from 850 to 2,350-nm, the absorption of water peaked around 1,900-nm and the fat tissue peaked around 2,300-nm [8]. Since the subcutaneous fat layer is composed of both water and adipose tissue, if the absorption rate of water and fat increases, the solubility of fat is high, increasing the therapeutic effect of laser-assisted lipolysis. Nevertheless, the reason why the wavelength more than 2,000-nm, which is higher than the fat absorption rate of the existing wavelengths, has not been used is because it is difficult to generate the desired wavelength technically and the higher risk of burn injury by high absorption rate of water in these wavelengths.

In this study, we used dual-wavelength laser system of 1,980 and 2,300-nm for lipolysis procedure. This Liposci system added the nonlinear optical nodule in the Nd:YAG system to generate the wavelength of 1,980-nm which has high absorption for water, and 2,300-nm which has high absorption for fat tissue. The synergy effect of each wave can be expected by using the dual-wavelength laser system, and this study has significance as the first attempt on the synergy effect of the dual-wavelength laser system. Since subcutaneous fat tissue is mixed with water and fat, the effect of lipolysis could be improved by targeting each component. To minimize the risk of damaging the other tissue but adipose tissue, we irradiated the laser with low frequency and power setting. Also, monitoring the abdomen tissue during the procedure with infrared camera, we could prevent the possible thermal injury of skin caused by high-absorption rate of energy. As a result, there was no complication regarding the thermal injury caused during the lipolysis procedure in this study.

Total 20 participants were first enrolled in this study and 1 participant was excluded later because of loss of follow-up. The results showed that the mean value of abdominal circumference decreased from the baseline at 1, 4, and 12 weeks after the lipolysis procedure, and all the differences were statistically significant. Especially the reduction rate was peaked at 4-week by –3.86%. In the result of ultrasound measurement, the mean value of subcutaneous fat thickness was also decreased from the baseline at 1, 4, and 12 weeks after the procedure and all of the differences were statistically significant. Among the reduction rates, the 12-week data was highest, showing –23.75% of reduction rate. When compared with the baseline, mean body weight increased by 0.06% in 1-week, decreased by –0.31% in 4-week, and decreased by –0.77% in 12-week result. However, all the differences were not statistically significant in body weight (Fig. 3).

Figure 3. The mean value of abdominal circumference and subcutaneous fat thickness decreased from the baseline at 1, 4, and 12 weeks after the lipolysis procedure, and all the differences were statistically significant (p < 0.05). However, all the differences of body weight were not statistically significant.

To sum up, both participants’ mean abdominal circumference and ultrasound-measured subcutaneous fat thickness decreased at 1, 4, 12-week follow-up with statistical significance, but the mean body weight showed no statistical significance. This means that the abdominal fat tissue was reduced after the lipolysis procedure regardless of the body weight change. Thus, this study could prove the effectiveness of the dual-wavelength laser system with 1,980 and 2,300-nm for lipolysis procedure by showing the statistically significant reduction of abdominal circumference and ultrasound data regardless of the body weight change (Fig. 3).

It was expected that the GAIS would increase as the abdominal circumference and ultrasound-measured subcutaneous fat thickness decreased over time, but the patient’s GAIS did not show a significant difference, and the surgeon’s GAIS increased at the 4-week and then decreased at the 12-week. For this reason, the GAIS is a subjective evaluation because it evaluates factors such as skin elasticity and overall body contour as well as abdominal circumference and ultrasound-measured subcutaneous fat thickness, which we are focusing on.

In conclusion, the dual-wavelength laser system with 1,980 and 2,300-nm for lipolysis procedure showed statistically significant efficacy on reducing abdominal circumference and subcutaneous fat thickness, and the safety of this laser system could be supported by low complication rate in this study model. More quantitative study would be further proposed to compare the overall effect between this innovative laser system and the conventional laser system for lipolysis procedure.

None.

Conceptualization: ESP. Data curation: KHA. Formal analysis: KHA. Funding acquisition: HGC. Investigation: HGC. Methodology: YJK. Project administration: ESP. Software: HGC. Validation: YJK. Visualization: YJK. Writing–original draft: YJK. Writing–review & editing: all authors.

Eun Soo Park is an editorial board member of the journal but was not involved in the review process of this manuscript. Otherwise, there is no conflict of interest to declare.

This work was supported by the Soonchunhyang University Research Fund (grant number: 2022-1219).

Contact the corresponding author for data availability.

None.