Thermodynamical Responses of the Living Skin Tissue With Two Temperatures and Thermal Heating due to Laser Pulse Type II

This in-depth study delves into the instantaneous thermoelastic behavior of living skin when subjected to transient laser pulses. It specifically employs a sophisticated nondissipative two-temperature Green–Naghdi model of Type II, a framework meticulously chosen for its ability to accurately capture complex thermal and mechanical interactions. The investigation comprehensively considers both radiative and thermal heating mechanisms, acknowledging their crucial roles in how laser energy interacts with biological tissue. To rigorously analyze these intricate responses, the research leverages the power of Laplace transforms, a mathematical technique well suited for solving transient problems. Through this analytical approach, the study meticulously explores the dynamic alterations occurring in several key physical parameters within the skin. These include displacement, which reflects the physical movement of tissue; strain, indicating deformation; temperature, a direct measure of thermal changes; and stress, representing internal forces within the material. A central focus of this research is to illuminate the profound influence of various laser parameters—such as pulse duration, energy density, and wavelength—on the resulting cutaneous response. This understanding is critical for predicting and mitigating potential thermal damage, a significant concern in many laser applications. The study places a strong emphasis on the concept of absorbed energy, recognizing it as the primary driver of the thermoelastic response. By carefully differentiating between thermodynamic and conductive temperatures, the research offers a more nuanced and accurate representation of heat transfer within the living tissue. This distinction is vital because it acknowledges the nonequilibrium nature of rapid heating processes, where the thermodynamic temperature may not instantaneously equate to the conductive temperature that dictates heat flow. This meticulous investigation significantly contributes to a more profound and comprehensive understanding pertinent to a wide array of medical and cosmetic laser applications. Such applications range from precision surgeries to esthetic treatments, where precise control over laser–tissue interaction is paramount. The insights garnered are particularly valuable in forecasting stress, strain, and, crucially, thermal damage during interventions like hyperthermia, a cancer treatment that uses heat to destroy tumor cells, or various forms of laser therapy aimed at tissue modification or removal. By providing a detailed mechanistic understanding, this research paves the way for optimizing laser protocols, enhancing treatment efficacy, and minimizing adverse side effects in clinical settings.