Structural design optimization and lipolytic effect prediction of vacuum suction cryolipolysis applicator: Simulation study.

BACKGROUND AND OBJECTIVES: Cryolipolysis is a popular noninvasive lipolytic method that uses low temperature to induce apoptosis or necrosis of adipocytes to reduce local fat in the human body. Vacuum suction applicator is a commonly used cryolipolysis equipment, which suction human skin and fat into a chamber for cooling. The structure of vacuum suction applicator is usually irregular, its cooling characteristic is also complex, and unreasonable suction structure will cause human discomfort. Biological experiments and clinical studies are often used to study the structural design of applicators, whereas these methods are impossible to obtain the three-dimensional cooling characteristic of applicator comprehensively and require a lot of costs. This study aims to optimize the structure of applicator for lowering discomfort, evaluate the cooling characteristic and lipolytic effect of applicators, which could provide guidance for clinical application of applicators and reduce costs.

MATERIALS AND METHODS: Cryolipolysis applicators models with four vacuum suction angles were established, and COMSOL was used to compare the cooling performance parameters, cooling kinetics, and lipolytic effects of the applicators. Specific evaluation indicators also include: cooling capacity analysis, temperature field analysis, lipolytic percentage, lipolytic volume, lipolytic weight, lipolytic thickness, lipolytic waistline, and lipolysis temperature threshold analysis.

RESULTS: The applicator with a small suction angle has a greater cooling capacity to cool deeper level of fat. When the cooling temperature is -10°C, the temperature of skin layer is about -10°C at 60 minutes, the temperature of fat layer is -7.36 to 3.01°C at 10 mm, -3.67 to 5.91°C at 20 mm and 2.01-10.81°C at 30 mm. The percentage of lipolytic declined with the increase of suction angle, the final lipolytic percentage (35.81%) of the 90° applicator is the highest, the percentage (28.72%) of 150° applicator (28.72%) is the lowest. The lipolytic volume, weight, and average thickness of applicator constantly increased with the increase of the suction angle, the final lipolytic volume range of the four suction angle applicators is 171.88-310.18 cm3 , the lipolytic weight range is 160.11-288.93 g, and the lipolytic average thickness range is 1.21-1.36 cm. Lower lipolysis temperature threshold will reduce the lipolysis effect, but it may also lead to another lipolysis mechanism-cell necrosis.

CONCLUSION: Different suction angles significantly affect the cooling characteristics and lipolytic effects of cryolipolysis applicator. A reasonable suction angle is one of the critical factors to improve the efficiency and comfort of cryolipolysis.