Abstract

Objectives: Monopolar radiofrequency (RF) devices utilize epidermal cooling to ensure safe dermal heating. While various cooling modalities have been explored, the specific impact of cooling algorithm design—including timing, frequency, and cumulative duration—on thermal behavior and dermal remodeling remains unclear. This study aimed to evaluate how different cooling control strategies influence intradermal thermal profiles, safety outcomes, and extracellular matrix (ECM) remodeling in a controlled porcine model. Introduction: Monopolar RF is a standard non-invasive procedure for skin tightening, achieved through controlled dermal heating and subsequent collagen remodeling. As cutaneous thermal injury is a function of time–temperature relationships, epidermal protection is critical during RF treatment. Beyond the cooling method itself, algorithmic parameters—such as the coordination of cooling sequences with RF pulses—may critically modulate thermal distribution and biological outcomes. However, preclinical evidence regarding these algorithm-dependent effects remains scarce. Materials / method: Three micro-pigs were treated with a monopolar RF system using two distinct cooling strategies: a conventional condensed sequence and an optimized expanded cooling sequence, each tested at two energy levels. Thermal responses were monitored via infrared thermography and ultrasound-guided intradermal temperature sensors at two depths. Safety was assessed through serial gross observation, serum chemistry, and histological analysis (H&E and NBTC staining). Dermal remodeling was quantified up to Day 30 using Masson’s trichrome, elastic fiber staining, and Collagen Type I immunohistochemistry. Stat Results: Both cooling strategies maintained safe surface temperatures and achieved effective intradermal thermal engagement without evidence of epidermal necrosis or systemic toxicity. Dermal remodeling markers significantly increased during the late post-treatment phase (Days 15–30). At Day 30, the optimized expanded cooling mode yielded a significantly higher collagen area fraction compared to the conventional mode at both energy levels. Elastic fiber area fraction and collagen type I expression also increased over time, with superior efficacy observed in the expanded cooling sequence. Conclusion: Cooling algorithm design is a critical determinant of the efficacy of dermal remodeling in monopolar RF treatment. While both modes ensured safety, the expanded cooling sequence significantly enhanced remodeling of collagen and elastic fibers. These findings suggest that cooling sequence parameters are mechanistically relevant determinants of remodeling efficacy and should be considered as critical design variables in monopolar RF systems.