Effect of geometric parameters of electrodes on skin heating for the design of non-ablative radiofrequency device.

BACKGROUND: Non-ablative radiofrequency (RF) has been widely used in clinical and at-home cosmetics devices. RF electrode geometry can influence the heat distribution in the tissue. This study analyzes the influence of geometric parameters of the electrode on the heat distribution in the layered tissue. MATERIALS & METHODS: The finite element simulation of the electrothermal coupling field was performed to obtain the three-dimensional (3D) temperature distribution of the four-layer tissue. The electrode geometric parameters including the inter-electrode spacing (5-12 mm), width (1-3 mm), length (3-10 mm), shapes (bar, dot and circle), and the coupling gel's electrical conductivity (0.2-1.5 S/m) were simulated. The maximum temperature at 2 mm depth (T-2 mm ) and the temperature difference (Tdiff ) between the maximum skin surface temperature and T-2 mm were obtained to evaluate the effectiveness and safety. RESULTS: The effect of geometric parameters on the effectiveness and safety was mixed. The maximum T-2 mm occurred with the 5 mm inter-electrode spacing, 3 mm width, 10 mm length, the circle-shaped electrode, and the 1.5 S/m coupling gel's electrical conductivity. The ratio of inter-electrode spacing to width at around four can achieve rapid temperature rise and skin surface temperature protection. The electrode shape influenced the area of temperature rise in the tissue's cross-section. The coupling gel's electrical conductivity should be close to that of the skin to avoid energy accumulation on the skin surface. CONCLUSION: The electrode's geometric parameters affect the effectiveness and safety of the RF product. This study has provided the simulation procedure for the electrode design.

A Three-dimensional Simulation Based on Radiofrequency Electrothermal Coupling fields for Skin Rejuvenation.

Radiofrequency (RF) current is used as an effective non-ablative method for skin rejuvenation. However, mixed results have been reported using different home-use RF devices. In order to evaluate the safety and effectiveness of home-use RF devices, this study has provided a three-dimensional (3D) simulation procedure based on the electrothermal coupling model for home-use RF devices. Firstly, the tissue geometric model with the setting electrode shapes was established and then imported into the simulation software. Secondly, electrical and thermal boundary conditions with excitation voltages were loaded to the corresponding components. In addition, the items of 3D temperatures at all locations and key temperatures of the tissue were assessed. The results have shown the temperature distributions of four commercial RF products, respectively. This 3D RF electrothermal coupling simulation can be conducted quickly and effectively to obtain the temperature and electric distribution of the home-use RF devices at different using periods, which is also useful for the design of home-use RF devices.Clinical Relevance- This study provides a simple and effective simulation procedure for device developers to evaluate the home-use RF devices when designing products. This simulation is also helpful for customer decision-making and performance evaluation considering different devices.

[The role of epithelial cells in the formation and development of nasal polyps].

Nasal polyps, as a subtype of chronic sinusitis, is prone to clinical recurrence and seriously affects the quality of life of patients, but its pathogenesis is unclear. It is considered to be a chronic inflammation of the nasal-sinus mucosa under the combined action of multiple factors. Among them, nasal mucosal epithelial injury and shedding are the main pathological features. Nasal-sinus epithelial separated nasal sinuses with the outside world, is the complex natural biological barrier to resist external stimuli and the key to maintaining homeostasis in the nasal sinuses. At present, the epithelium is considered not only as a "target organ" but also as an "effector" and a central regulator of the inflammatory response. This paper reviews the role of epithelial cells in the formation and development of nasal polyps, including the epithelial cell layer were stimulated not only leads to tissue remodeling, changes in mucociliary clearance, abnormal ion channels, and proliferation and apoptosis imbalance, but also produce a series of bioactive substances in response to various internal and external stimuli.Therefore, maintaining the integrity of the structure and function of airway mucosal epithelial cells may be a new approach for clinical prevention and treatment of nasal polyps.