Thermophysical and mechanical properties of biological tissues as a function of temperature: a systematic literature review.

Background: Detailed information on the temperature dependence of tissue thermophysical and mechanical properties is pivotal for the optimal implementation of mathematical models and simulation-based tools for the pre-planning of thermal ablation therapies. These models require in-depth knowledge of the temperature sensitivity of these properties and other influential terms (e.g., blood perfusion and metabolic heat) to maximize the treatment prediction outcome.

Methodology: A systematic literature review of experimental trials investigating thermophysical and mechanical properties of biological media, as well as blood perfusion and metabolic heat, as a function of temperature in hyperthermic and ablative thermal range, was conducted up to June 2021.

Results: A total of 61 articles was selected, thus enabling a comprehensive overview of the temperature dependence of thermophysical properties (i.e. thermal conductivity, specific heat, volumetric heat capacity, density, thermal diffusivity), and mechanical properties (shear, elastic, storage, loss and complex moduli, loss factor, stiffness) along with the principal measurement techniques. The reviewed studies considered different tissues, e.g., liver, fat, cartilage, brain, myocardium, muscle, bone, skin, pancreas tissues, and also some tumorous tissues.

Conclusions: The thermophysical properties of soft tissues appear rather constant until 90 °C, with slight differences ascribable to tissues characteristics and measurement methods. Conversely, the information on mechanical properties is heterogeneous because most of the articles investigated different types of properties in different biological tissues. Furthermore, most of the experiments were conducted ex vivo; only a small percentage concerned in vivo studies. Limited recent information about the temperature dependence of metabolic heat and blood perfusion was observed.