A Modified Transmission Line Modelling Approach for Bioheat Transfer

This study presents a modified Transmission Line Modelling (TLM) method for simulating bioheat transfer in biological tissues, with a particular focus on accounting for non-unidirectional blood flow. While the Pennes bioheat equation has been widely used for such problems, it assumes unidirectional perfusion and may overlook important thermal effects introduced by non-unidirectional blood flow. To address this limitation, a TLM-based formulation of the Klinger bioheat equation known for incorporating flow directionality is developed and implemented for one-dimensional (1D) problems. A novel TLM cell model is introduced to represent the governing equation and its associated boundary conditions. Validation is performed through a 1D multilayer human tissue model exposed to electromagnetic (EM) fields at multiple 4G carrier frequencies. Comparative results with the Finite Element Method (FEM) show strong agreement, especially under steady-state conditions. Furthermore, the proposed model reveals that the impact of non-unidirectional blood flow becomes more pronounced in thicker tissue layers, confirming the importance of incorporating convective terms. This work demonstrates that the modified TLM approach provides a stable, efficient, and more physiologically accurate method for bioheat simulations.