Fractional-order thermo-biophysical modeling of soft tissues: analytical, numerical, and experimental insights for thermal therapies
摘要
Accurate prediction of temperature distribution within biological tissues is essential for ensuring the safety and effectiveness of thermal therapies, such as laser ablation, radiofrequency ablation, and hyperthermia. Classical bioheat formulas, such as Pennes’ equation, are based on the assumption of an instantaneous heat propagation and local thermal equilibrium, and are limited in their capacity to capture the memory-dependent and non-local heat transmission found in heterogeneous soft tissues.
ObjectiveThe present work proposes and analyzes a fractional-order bioheat transfer model that extends classical and non-Fourier formulations to more accurately describe realistic thermal transport in biological tissues, combining analytical, numerical and experimental studies to improve thermal therapy modeling.
Materials and methodsA one-dimensional (1D) transient fractional-order bioheat equation was derived and solved using Laplace transforms with numerical inversion to analyze temporal temperature evolution. The model was then extended to a two-dimensional (2D) steady-state configuration, solved using an iterative Gauss–Seidel method under defined boundary conditions. Ex-vivo thermal properties—thermal diffusivity (D), thermal conductivity (k), and volumetric heat capacity (Ch)—were experimentally measured for bovine heart, liver, and kidney tissues at room temperature (21 ~ 25 °C) and incorporated as model inputs. Model predictions were compared with those of the classical Pennes, Cattaneo–Vernotte (CV), and dual-phase lag (DPL) formulations bioheat models.
ResultsThe fractional-order model reproduced delayed thermal response and experimentally consistent cooling profiles in agreement with the experimental data, and showed lower quantitative errors (RMSE < 0.42 °C, MAE < 0.35 °C) with respect to other models. Measured thermal properties across tissues were comparable—D ≈ 0.15 mm²/s, k ≈ 0.5 W/(m·K), and Ch between 3.4 and 3.7 MJ/m³·K— confirming comparable thermophysical properties across the investigated tissues within experimental uncertainty.
ConclusionsThe proposed fractional-order bioheat framework provides a unified and flexible extension of existing bioheat models, effectively capturing anomalous and memory-dependent heat conduction in soft tissues. The approach establishes a foundation for clinically relevant thermal therapy modeling and can be readily extended to temperature-dependent properties, convective boundary conditions, and real-time imaging integration for treatment planning and optimization.