Models for thermal damage in tissues: processes and applications

Irreversible thermal alterations in tissue function and structure are used in clinical applications to achieve diverse goals, from lower-temperature tumor ablation to higher-temperature tissue fusion and surgical cutting. The typical formulation in tumor hyperthermia studies, the thermal iso-effect dose, derives from cell-survival studies but describes a single process only over a limited range of temperatures and is thus not suitable for multiple higher-temperature events. Many other thermal damage processes have been described using the Arrhenius kinetic rate of formation approach, which has the advantage that it is inherently quantitative in nature and can easily be compared with quantitative markers of injury or histologic section. The vast majority of Arrhenius studies have been directed toward measurable cellular effects at relatively low temperatures. Some emphasis in this paper has been placed on what is known of higher-temperature processes to support the theme of this issue. This review compares and contrasts the two thermal-damage formulations and reviews methods to convert between them.