## 2 Mechanism of Action
TCPs allow for detailed treatment planning, pulse consistency, and multi-point focus, making it possible to treat large or complex areas efficiently. TCPs play a vital role by heating collagen fibrils to 60-70 \({}^{\circ}\)C, forming localized thermal [25; 26]. These temperatures are optimal for collagen contraction and denaturation, which initiates an immediate lifting effect. During the second phase of wound healing, new collagen forms, critical for tissue remodeling. Between 48 h and 10 weeks after treatment begins, inflammation stimulates collagen production, fibroblast proliferation, and elastin generation around the TCPs. By day 28, the dermis shows increased elasticity and structural integrity. The phases of TCP-induced collagen remodeling are illustrated in Figure 4.  
At ten weeks post-treatment, newly formed collagen replaces existing collagen in the treated area, providing further skin lifting and tightening, with this remodeling effect potentially continuing for up to a year [34; 35]. Each treatment line delivers multiple TCP  
Figure 4: Phases of TCP-induced collagen remodeling: inflammation, proliferation, maturation, and remodeling. points, with the energy, strength, and size of each point adjustable according to the area being treated. The machine's handles incorporate critical safety features to ensure effective treatment, preventing discomfort and injury for patients. Each handle includes temperature control sensors that continuously monitor heat levels, ensuring they stay within safe limits. If temperatures approach unsafe levels, these sensors automatically adjust energy output to prevent burns and maintain patient comfort. Additionally, the handles feature a stuck-point detection and alert system, designed to prevent hazards from prolonged energy delivery to a single area. Occasionally, a handle may stay in the same position due to user error, mechanical malfunction, or unintentional immobilization, which can lead to concentrated energy exposure in one spot and potentially cause burns or tissue injury. To mitigate this risk, the handles are equipped with sensors that track movement and monitor positioning, allowing for the detection of any potential stuck points. If a stuck point is identified, the system activates a visual and audible alarm, halts energy delivery, and alerts the clinician to reposition the handle and perform a mechanical check. This feature is crucial, not only to prevent overheating but also to enhance patient safety by protecting surrounding skin tissues. These safety measures ensure that HIFU treatments remain non-invasive, delivering consistent energy distribution for optimal treatment outcomes. A schematic overview of the More Young HIFU machine is shown in Figure 5.  
Moreover, the machine's handles incorporate essential safety measures to ensure effective treatment while preventing discomfort and injury. Each handle is equipped with temperature control sensors that continuously monitor heat levels, keeping them within safe limits. If temperatures reach unsafe levels, these sensors automatically adjust the energy output to protect against burns and discomfort, enhancing patient safety throughout the procedure. Another critical safety feature is the stuck-point detection and alert system, designed to prevent hazards that may arise from prolonged energy delivery to a specific skin area. Figure 5: More Young HIFU machine. Occasionally, the handle may remain in the same position due to user error, mechanical malfunction, or accidental immobilization, causing an excessive concentration of power waves in one area, which can lead to burns and tissue injury. The system uses sensors to track movement and monitor the handle's position, allowing it to detect any potential stuck point. If a stuck point is identified, the system activates a visual and audible alarm, halts energy delivery, and alerts the clinician to adjust the handle and perform a mechanical check.