Use of 3 D geometrical models to improve efficacy and safety of Laser-assisted liposuction : a prospective study

Article received November 25, 2014. Article accepted June 07, 2015. Introduction: On the basis of the available information, it is difficult to establish the appropriate dose of laser energy with which to obtain predictable results in laser-assisted liposuction. The purpose of this study is to evaluate the safety and efficacy of a 980-nm diode laser by using geometrical formulas. These formulas allow a precise quantification of tissue volume and, as a result, an estimation of the required laser dose. Methods: This prospective study was conducted to evaluate 39 consecutive patients who underwent 980-nm diode laser-assisted liposuction (LAL) between November 2011 and November 2013. Four geometric patterns were used to determine the volume of fat before laser application. Ultrasonography was used to determine fat depth. Biopsies were conducted to determine immediate laser tissue reaction relative to laser dose. The aesthetic results and complications were recorded. Pearson’s correlation coefficient was used to determine the relationship between the applied energy and tissue volume. Results: 163 anatomic regions were treated with 980-nm LAL. The applied energy was relative to the volume in each area (R = 0.8786). 8 to 14 J/ cm3 was the dose needed to produce effective hemostasis and minimal lipolysis. The results were very satisfactory in most cases. Biopsy results revealed lipolysis, ballooning, membrane rupture, and collagen band breakage; these changes varied with the radiation dose. The only complications were edema and transient bruising. Conclusion: The use of 3D geometrical models improved safety and efficacy of laser-assisted liposuction by permitting accurate determination of the tissue volume. ■ ABSTRACT


INTRODUCTION
Laser-assisted liposuction (LAL) allows hemostasis, lipolysis, and good skin retraction with low morbidity in the hands of experienced surgeons.However, there are difficulties in establishing the dose of energy to be applied on the tissues to obtain predictable results 1,2 .Different methods to quantify the fat volume reduction have been proposed to determine optimal dosage or to improve dosimetry for laser lipolysis.In 2006, Kim and Geronemus 3 reported the evaluation of fat volume reduction using MRI.In 2008, Mordon et al. 4 proposed a mathematical model of laser lipolysis and assessed the reduction of volume using a photographic analysis similar to the technique described by Lowe et al.

OBJECTIVE
The purpose of the present prospective study was to evaluate the safety and efficacy of a 980-nm diode laser with a new technique that allows quantification of the fat volume and estimation of the required dose of laser energy using three-dimensional geometrical models.In the current report, we describe the threedimensional laser assisted lipoplasty procedure and review the results of 136 consecutive procedures.

Patient Selection
Between November 2011 and November 2013, 980-nm diode LAL was performed in 39 patients (30 women and 9 men) using four geometric patterns.
The series included patients with normal or reduced skin elasticity; a body mass index (BMI) between 18.6 and 29.9; one or more regions to be treated; irregularities in the treatment area (e.g., cellulite); and small regions to be treated, such as the neck, pubis, or knees.Lipoplasty was performed in combination with other surgical procedures in 33 cases (85%).
Patients were excluded if they were younger than 18 years, pregnant, breastfeeding, or smokers.Also excluded were patients with a BMI ≥ 30 (obesity) or ≤ 18.5 (underweight), unrealistic expectations, cardiovascular disease, diabetes, coagulopathy, or other major comorbid diseases.

Preoperative Evaluation
Preoperative evaluation consisted of routine laboratory tests, cardiology evaluation, and standardized photographs.Additionally, all patients signed informed consent in accordance with the basic principles of the Helsinki Declaration of Rights.
On the day before surgery, the following were performed: marking, measurement of the tissue thickness using ultrasonography, and estimation of the fat volume and energy to irradiate the treated regions.

Marking
Surface marking of the treated regions was performed by selecting the three-dimensional geometric shape that was more suitable to the anatomical region and corresponded to a trapezoidal parallelepiped, rectangular parallelepiped, spherical segment, or hemiellipsoid shape.A trapezoidal parallelepiped was used in most cases.Hemiellipsoid or spherical segments were used in the trochanteric area, inner thighs, and breast.One or two patterns were used in each region according to its size.For example, rectus abdominis muscle regions were subdivided into 3 small parts using rectangular and trapezoidal parallelepipeds (Figure 1A).

Ultrasonography
The thickness of the subcutaneous fat was evaluated in all cases using an ultrasound transducer of 7.5 MHz from the subcutaneous fat to the muscle fascia on each region; an average in centimeters was used in the formulas (Figure 1B).The surgeon took all measurements to be sure they were consistent in order to reduce relative and percent error.

Laser Equipment
A 980-nm diode laser device (Lumiia Sonobeam T, Buenos Aires, Argentina) with integrated ultrasound was used to measure and treat all patients.The laser irradiation is applied with a 600-µm fiberoptic that passes through a 1.5-or 3-mm cannula with an opening at the tip, from which the fiber protrudes 2 to 4 mm.The temperature was monitored during the laser application with a non-contact infrared laser-point digital thermometer.

Anatomic pathology
The areas for biopsy sampling were defined and the tissue volume was measured using the described geometric models.Biopsy specimens were obtained approximately 1 hour after laser application in dermolipectomy flaps to assess the immediate tissue reaction related to the dose.The samples were examined by two pathologists.Twenty-seven irradiated surgical specimens with different values (7, 10, 15, 20,  30, and 50 J/cm³) of applied energy were analyzed.

Geometric Models and Mathematical Formulas
We considered that a succinct definition was necessary for the geometric patterns applied: a twodimensional figure is formed by surfaces, areas, or sides that could be a circle, an ellipse, or a parallelogram, each corresponding to a surface of a three -dimensional figure.
The three-dimensional figures used were as follows: rectangular parallelepiped, trapezoidal parallelepiped, segment of a sphere and hemiellipsoid 5 (Figure 2 A-D).The mathematical formulas of these four geometric models were as follows: 1) Rectangular parallelepiped A parallelepiped is a polyhedron with six faces, which is limited by three pairs of planes.A rectangular parallelepiped is a figure formed by three pairs of parallel planes in which all angles are right angles (Figure 2A).  3) Spherical segment The spherical segment is defined as a portion of a sphere cut out of the center plane (Figure 2C).The formula for the volume of a spherical segment is as follows: V = π/6 × (3 × r1² + h²) × h, where V = volume, π = 3.14159, r1 = radius, and h = height.The simplified formula to calculate the tissue volume of this figure is as follows: V = [0.5233× (3 × r1² + h²) × h] + S, where V = volume, r1 = radius of the segment in cm, h = height of the segment in cm, and S = volume of infiltrated tumescent solution in cm 3 .4) Hemiellipsoid An ellipsoid is a three-dimensional figure in which all plane sections are ellipses.A hemiellipsoid is either of the halves into which an ellipsoid is divided by a plane of symmetry.To calculate the volume, the semiaxes a, b, and h must be measured.Each semiaxis is equal to half the length of the axis (expressed in cm) and corresponds to the radius of a sphere; semiaxis h is represented by the height or greatest depth from the skin to the muscular fascia (Figure 2D).The simplified formula to calculate the tissue volume of the hemiellipsoid is as follows: V =

Operative Technique
Prior to the procedure, 1 g cefazolin was administered intravenously as antibiotic prophylaxis.The infiltration of the tumescence saline solution was performed at room temperature (74.3°F or 23.5°C on average) with 0.05% to 0.1% lidocaine and epinephrine 1:1,000,000.The infiltrated volume was added to the estimated volume in the corresponding formula 6 .
In most cases (139 of 163 [85%]), each region was irradiated before liposuction until the estimated dose for effective hemostasis was reached.
Laser liposuction cannulas of 1.5 mm were used in the face and neck, and cannulas of 3 mm were used in the body, depending on the tissue thickness.The doses of radiation ranged from 5 to 15 J/cm³, depending on the region being treated (Table 1).The range of power used in each region was as follows: 10-15 watts (W) in the face; 10-20 W in the neck; 15-25 W in the arms, thighs, and knees; and 20-35 W in the abdomen.The hand movement speed was practically the same, 40.1 cm/sec average for each area treated by the same surgeon to achieve an even distribution inside each area.
All patients were discharged from the hospital on the day of surgery 1 .We left some liposuction incisions open to facilitate drainage.For abdominoplasties and neck lifts, we used Jackson Pratt drains, which were removed between 2 and 5 days postoperatively.

Postoperative Instructions
Postoperative instructions included the following: early mobilization, adequate hydration, normocaloric diet, cephalexin and ketorolac regimen for 4 days, diclofenac for 10 to 14 days, return to usual activities between 7 and 14 days, and compressive elastic garment(s) for 6 to 10 weeks.

RESULTS
The average age of the patients in this series was 41 years (range, 19-63 years).The average length of follow-up was 15 months (range, 3-27 months).
There was a strong positive correlation between the applied energy and the volume of infiltrated tissue evaluated by Pearson's correlation coefficient (R = 0.8786) (Figure 3).
Table 1 summarizes the 163 anatomic regions treated with 980-nm LAL, the average volume before and after infiltration with tumescent solution, the aspirated volume, and the dose of laser irradiation.
A 5-point global aesthetic improvement scale (GAIS) was used to assess the opinion of the patients, whereas two surgeons reviewed the pre-and   and 8).There were no major or relevant complications, such as hematomas, seromas, wound dehiscence, infections, burns, skin necrosis, or irregularities.
Mild to moderate edema and mild transient ecchymosis were observed in most cases, but these effects subsided within 4 weeks with non-steroidal antiinflammatory drugs (NSAIDs).Mild to moderate pain was observed in the first 15 days, but this effect likewise subsided with NSAIDs.A 60-year-old male patient (2.56%) who underwent extensive liposuction with 10 J/cm 3 irradiation in the abdomen and no irradiation in the pubic area had significant bruising in the scrotal region and edema for 4 weeks, as well as moderate infraumbilical edema up to 8 weeks.These effects also subsided with NSAIDs.
The surgery time slightly increased in the initial cases because of the measurements made during surgery.
The anatomic pathological reports showed the following in samples irradiated with 10 or more J/cm 3 : lipolysis, adipocyte ballooning, and focal or diffuse adipocyte membrane rupture.No bleeding foci were observed in these samples.In samples irradiated with 15 or more J/cm 3 , the following were noted: extensive lipolysis and more adipocyte membrane rupture than ballooning, broken collagen bands (due to thermal effects) were observed, but no epidermal detachment was noted (Figure 9).

Case Examples
The following three cases exemplify the use of geometric patterns in different regions.

Case 2
A 60-year-old man presented with gynecomastia with moderate to severe skin flaccidity.Here, we used a spherical segment that corresponded approximately to the shape of the irradiated tissue, with the patient in supine position.The 6-cm radius included the entire breast region.The dose used to remove almost pure fat, with minimal blood loss, was 7.78 J/cm 3 .The tissue volume calculation was as follows: V = [0.5233× (3 × r1² + h²) × h] + S = [0.5233× (3 × 6² cm+ 1² cm) × 1] + 200 cm 3 = 257 ± 0.3 cm 3 .The dose applied to each breast was therefore 2000 J/257 cm 3 = 7.78 J/cm 3 .As shown in Figure 6, the shape and skin retraction improved after surgery.
Before comparing our results with previous reports we would like to clarify some points to avoid semantic confusions: First, we refer to laser-assisted liposuction instead of laser lipolysis, which is fat removed by liposuction.This means we don't pursue to reduce fat by extensive laser lipolysis.On the contrary, we believe that very high doses must be avoided, particularly when several large areas are treated.Fat reduction by laser  lipolysis with high doses should be limited only to small areas.Our goal was to avoid extensive burning of tissue and to minimize complications, reducing the dose to the minimal effective for an optimal hemostasis 19 .
Second, to the best of our knowledge, 3-D geometrical patterns have never been proposed for fat volumetry.The use of these patterns permits us to define tissue volume in every area for any possible treatment.
In the submental zone, Kim and Geronemus 3 reported that approximately 3000 J needs to be applied to get a mean volume reduction of 5.2 ± 2.8 cm 3

Figure 1 .
Figure 1.A -Marking before abdominoplasty and 980-nm diode LAL: note the rectus abdominis muscle anatomical region subdivided into three parallelepipeds, and the marked dermolipectomy flap for biopsy (segments A to F) (Left); B -Ultrasonography image showing fat thickness measured in mm over the rectus abdominis muscle (RAM) (Right).In the epigastric region delimited by a trapezoid, the tissue volume calculation without infiltration was as follows: V = (a + a '/2) × (b + b '/2) × h = (11 cm + 9 cm)/2 × (3 cm + 9 cm)/2 × 1.5 cm = 90 ± 0.2 cm 3 The simplified mathematical formula to calculate the tissue volume of this figure is as follows: V = (a × b × h) + S, where V = volume; a, b = lengths of the sides of the figure measured in cm.h = depth of fat in cm, and S = volume of infiltrated tumescent solution in cm 3 .

Figure 2 .
Figure 2. A -Rectangular parallelepiped (Above, left); B -Trapezoidal parallelepiped (Above, right); C -Spherical segment (Below, left); D -Hemiellipsoid (Below, right).2) Trapezoidal parallelepiped The trapezoidal parallelepiped is a threedimensional figure in which two faces are trapezoids and four faces are parallelograms (Figure 2B).The simplified mathematical formula to calculate the tissue volume of this figure is as follows: V = [(a + a '/2) × (b + b '/2) × h] + S, where V = volume; a, a ', b, b' = lengths of the sides of the figure in cm; h = height or depth in cm; and S = cm 3 of infiltrated tumescent solution.3)Spherical segment The spherical segment is defined as a portion of a sphere cut out of the center plane (Figure2C).The formula for the volume of a spherical segment is as follows: V = π/6 × (3 × r1² + h²) × h, where V = volume, π = 3.14159, r1 = radius, and h = height.The simplified formula to calculate the tissue volume of this figure is as follows: V = [0.5233× (3 × r1² + h²) × h] + S, where V = volume, r1 = radius of the segment in cm, h = height of the segment in cm, and S = volume of infiltrated tumescent solution in cm3 .4) Hemiellipsoid An ellipsoid is a three-dimensional figure in which all plane sections are ellipses.A hemiellipsoid is either of the halves into which an ellipsoid is divided by a plane of symmetry.To calculate the volume, the semiaxes a, b, and h must be measured.Each semiaxis is equal to half the length of the axis (expressed in cm) and corresponds to the radius of a sphere; semiaxis h is represented by the height or greatest depth from the skin to the muscular fascia (Figure2D).The simplified formula to calculate the tissue volume of the hemiellipsoid is as follows: V = [4.186× 0.5 × (a × b × h)] + S = [2.093× (a × b × h)] + S, where V = volume; a, b, and h = length of semiaxes in cm; and S = volume of infiltrated tumescent solution in cm 3 .

Figure 3 .
Figure 3. Pearson's correlation coefficient was used to determine the relationship between the applied energy and tissue volume.The applied energy was relative to the volume in each area (R = 0.8786).

Figure 9 .
Figure 9. Biopsy samples stained with hematoxylin-eosin, viewed under optic microscopy at 100x magnification.A -Tissue irradiated with 10 J/cm 3 : note the adipocyte ballooning, rupture of membranes, and vascular preservation (Left); B -Sample of biopsy irradiated with 15 J/cm 3 : note the extensive lipolysis with ruptured adipocyte membranes (Right).

Bukret WE et al. www.rbcp.org.brTable 1 .
Summary of the 163 anatomical regions treated with 980-nm LAL; the volume before and after infiltration with tumescent solution, and the aspirated volume measured in cm 3 ; the dose of laser irradiation related to infiltrated volume measured in J/cm 3 , and the total dose applied in each area (average values are shown for all data).