Abstract：So far there is no uniform specification for some design parameters of bipolar radiofrequency (RF) devices for noninvasive treatment of local fat accumulation. In this work,the finite element method and external experiment were used to analyze the influence of different parameters on the fat melting effect of tissues in bipolar RF,seeking for the fat melting configuration with a large range of fat melting effect without causing thermal damage to skin layer as far as possible. The finite element analysis of thermoelectric coupling of biological tissues was carried out by COMSOL Multiphysics. To verify the validity of the model,a self-developed single-channel bipolar RF output device was used to perform RF output of pig abdominal tissues. The results of finite element analysis showed that the final temperature of the skin layer was lower than the thermal damage threshold temperature and part of the fat layer was in the thermal damage area under the fat melting configuration with the power of 10 W,the diameter of the electrode sphere of 3,5,8 mm and electrode spacing of 2 and 3 cm after 30 min heating with bipolar RF;the domain point probe showed that the temperature curve in the thermal damage area of the fat layer met the requirement of the fat melting temperature. The temperature distribution in tissues under bipolar RF heating was significantly affected by different fat melting configurations. At a power of 10 W,when using a spherical electrode with a diameter of 8 mm and pressing the skin to a depth of 1 mm,under the condition of electrode spacing of 2 and 3 cm,the largest area of continuous thermal damage area and spot-shaped thermal damage area within the fat layer will be generated,and the area of thermal damage area is 2.84 and 2.55 cm2,respectively.External experiments with the same fat melting configuration showed that the final temperature of the thermocouple probe at the same position as the tissue model was 0.92±0.43℃ different from that of the corresponding domain point probe. The finite element analysis results were consistent with the experimental results. According to the results of simulation and experimental validation,the above configuration made the bipolar RF not cause thermal damage to the skin layer,at the same time while generate effective thermal damage area in the fat layer. The temperature in the thermal damage area could meet the requirement of the fat melting temperature. The reasonableconfiguration is a critical factor for the success of bipolar RF fat melting.
臧连儒, 周宇, 康佳林, 海潇, 李媛, 薛音闽. 电极间距与电极直径对恒功率下双极射频熔脂效果影响的研究[J]. 中国生物医学工程学报, 2020, 39(5): 566-576.
Zang Lianru, Zhou Yu, Kang Jia, Lin Haixiao, Li Yuan, Xue Yinmin. Study on the Effect of Electrode Spacing and Electrode Diameter on Bipolar Radiofrequency Fat Melting at Constant Power. Chinese Journal of Biomedical Engineering, 2020, 39(5): 566-576.
[1] Mulholland RS,Paul MD,Chalfoun C.Noninvasive body contouring with radiofrequency,ultrasound,cryolipolysis,and low-level laser therapy[J].Clinics in Plastic Surgery,2011,38(3):503-520. [2] Gold MH,Khatri KA,Hails K,et al.Reduction in thigh circumference and improvement in the appearance of cellulite with dual-wavelength,low-level laser energy and massage[J].J Cosmet Laser Ther,2011,13(1):13-20. [3] Jewell ML,Baxter RA,Cox SE,et al.Randomized sham-controlled trial to evaluate the safety and effectiveness of a high-intensity focused ultrasound device for noninvasive body sculpting[J].Plastic and Reconstructive Surgery,2011,128(1):253-262. [4] 李丽,向海炼,杨文斌,等.脂肪堆积治疗进展[J].中国激光医学杂志,2018(3):232-238. [5] Kennedy J,Verne S,Griffith R,et al.Non-invasive subcutaneous fat reduction:A review[J].Journal of the European Academy of Dermatology and Venereology,2015,29(9):1679-1688. [6] Weiss RA.Noninvasive radio frequency for skin tightening and body contouring[J].Semin Cutan Med Surg,2013,32(1):9-17. [7] Kaplan H,Gat A.Clinical and histopathological results following TriPollarTM radiofrequency skin treatments[J].Journal of Cosmetic and Laser Therapy,2009,11(2):78-84. [8] Anolik R,Chapas AM,Brightman LA,et al.Radiofrequency devices for body shaping:A review and study of 12 patients[J].Seminars in Cutaneous Medicine and Surgery,2009,28(4):236-243. [9] Friedmann DP.A review of the aesthetic treatment of abdominal subcutaneous adipose tissue:background,implications,and therapeutic options[J].2015,41(1):18-34. [10] Sadick NS,Makino Y.Selective electro-thermolysis in aesthetic medicine:A review[J].Lasers in Surgery and Medicine,2004,34(2):91-97. [11] Fleishman S D,Whayne J G,Panescu D,et al.In vitro study of lesion size dependence on electrode geometry during temperature-controlled radiofrequency ablation[C]//International Conference of the IEEE Engineering in Medicine &Biology Society.Baltimore:IEEE,1994:790-791. [12] Araújo ARD,Soares VPC,Silva FSD,et al.Radiofrequency for the treatment of skin laxity:mith or truth[J].Anais Brasileiros de Dermatologia,2015,90(5):707-721. [13] Joel JL,Paulino VJ,Rox A,et al.Selective and localized radiofrequency heating of skin and fat by controlling suRFace distributions of the applied voltage:analytical study[J].Physics in Medicine &Biology,2012,57(22):7555-7578. [14] Pennes HH.Analysis of tissue and arterial blood temperatures in the resting human forearm[J].Journal of Applied Physiology,1998,85(1):5-34. [15] Berjano EJ.Theoretical modeling for radiofrequency ablation:state-of-the-art and challenges for the future[J].2006,5(1):24-24. [16] Mirrashed F,Sharp JC,Krause V,et al.Pilot study of dermal and subcutaneous fat structures by MRI in individuals who differ in gender,BMI,and cellulite grading[J].Skin Research and Technology,2004,10(3):161-168. [17] Boisnic S,Divaris M,Nelson AA,et al.A clinical and biological evaluation of a novel,noninvasive radiofrequency device for the long-term reduction of adipose tissue[J].Lasers Surg Med,2014,46(2):94-103. [18] Kwon T,Kim JH,Joon S,et al.Assessment of equivalence of adipose tissue treatment with a noncontact field RF system delivering 200 W for 30 min and 300 W for 20 min:An in vivo porcine study[J].Laser Therapy,2017,26(1):39-52. [19] Jimenez Lozano JN,Vacas-Jacques P,Anderson RR,et al.Effect of fibrous septa in radiofrequency heating of cutaneous and subcutaneous tissues:Computational study[J].Lasers in Surgery and Medicine,2013,45(5):326-338. [20] Moritz AR.Studies of thermal injury:I.The conduction of heat to and through skin and the temperatures attained there-in:A theoretical and an experimental investigation[J].American Journal of Pathology,1947,23(4):530-549. [21] Moritz AR,Henriques FC.Studies of thermal injury:II.The relative importance of time and surface temperature in the causation of cutaneous burns[J].Am J Pathol,1947,23(5):695-720. [22] Weaver JA,Stoll AM.Mathematical model of skin exposed to thermal radiation[J].Aerosp Med,1969,40(1):24-30. [23] Haemmerich D,Schutt DJ,Dos SI,et al.Measurement of temperature-dependent specific heat of biological tissues[J].Physiol Meas,2005,26(1):59-67. [24] Bhattacharya A,Mahajan RL.Temperature dependence of thermal conductivity of biological tissues[J].Physiological Measurement,2003,24(3):769-783. [25] Xu F,Lu T.Introduction to Skin Biothermomechanics and Thermal Pain Ⅱ:Skin Mechanical Behaviour[M]//Berlin:Science Press Beijing and Springer-Verlag,2011:33-33. [26] Segura S,Requena L.Anatomy and histology of normal subcutaneous fat,necrosis of adipocytes,and classification of the panniculitides[J].Dermatologic Clinics,2008,26(4):419-424. [27] Wilson SB,Spence VA.A tissue heat transfer model for relating dynamic skin temperature changes to physiological parameters[J].Physics in Medicine and Biology,1988,33(8):895-912. [28] Gabriel S,Lau RW,Gabriel C.The dielectric properties of biological tissues: Measurements in the frequency range 10 Hz to 20 GHz[J].Physics in Medicine and Biology,1996,41(11):2251-2269. [29] González-Suárez A,Gutierrez-Herrera E,Berjano E,et al.Thermal and elastic response of subcutaneous tissue with different fibrous septa architectures to RF heating:Numerical study[J].Lasers in Surgery &Medicine,2015,47(2):183-195. [30] Franco W,Kothare A,Ronan SJ,et al.Hyperthermic injury to adipocyte cells by selective heating of subcutaneous fat with a novel radiofrequency device:Feasibility studies[J].Lasers in Surgery and Medicine,2010,42(5):361-370. [31] Franco W,Kothare A,Goldberg DJ.Controlled volumetric heating of subcutaneous adipose tissue using a novel radiofrequency technology[J].Lasers in Surgery and Medicine,2009,41(10):745-750.
