An advanced computational bioheat transfer model for a human body with an embedded systemic circulation

Abstract

In the present work, an elaborate one-dimensional thermofluid model for a human body is presented. By contrast to the existing pure conduction-/perfusion-based models, the proposed methodology couples the arterial fluid dynamics of a human body with a multi-segmental bioheat model of surrounding solid tissues. In the present configuration, arterial flow is included through a network of elastic vessels. More than a dozen solid segments are employed to represent the heat conduction in the surrounding tissues, and each segment is constituted by a multilayered circular cylinder. Such multi-layers allow flexible delineation of the geometry and incorporation of properties of different tissue types. The coupling of solid tissue and fluid models requires subdivision of the arterial circulation into large and small arteries. The heat exchange between tissues and arterial wall occurs by convection in large vessels and by perfusion in small arteries. The core region, including the heart, provides the inlet conditions for the fluid equations. In the proposed model, shivering, sweating, and perfusion changes constitute the basis of the thermoregulatory system. The equations governing flow and heat transfer in the circulatory system are solved using a locally conservative Galerkin approach, and the heat conduction in the surrounding tissues is solved using a standard implicit backward Euler method. To investigate the effectiveness of the proposed model, temperature field evolutions are monitored at different points of the arterial tree and in the surrounding tissue layers. To study the differences due to flow-induced convection effects on thermal balance, the results of the current model are compared against those of the widely used modelling methodologies. The results show that the convection significantly influences the temperature distribution of the solid tissues in the vicinity of the arteries. Thus, the inner convection has a more predominant role in the human body heat balance than previously thought. To demonstrate its capabilities, the proposed new model is used to study different scenarios, including thermoregulation inactivity and variation in surrounding atmospheric conditions.

Robust Finite Element Approaches to Systemic Circulation Using the Locally Conservative Galerkin (LCG) Method

“…Further details on boundary conditions may be obtained from references (Mynard and Nithiarasu 2008;Low et al, 2012;Coccarelli and Nithiarasu 2015;?, Coccarelli et al, 2016).…”

“…The physical model consists of a network of elastic tubes representing blood flow in large arteries, i.e., 63 arteries including the coronaries (Mynard and Nithiarasu, 2008;Low et al, 2012;Coccarelli and Nithiarasu, 2015;Boileau et al, 2015;Coccarelli and Nithiarasu, 2015;Coccarelli et al, 2016). To represent the arterial system, the model proposed by (Mynard and Nithiarasu, 2008;Low et al, 2012) is adopted and for 63 arterial segments are used as shown in Fig.…”

“…6 may produce instability due to the presence of the first order derivative of F. Thus, upwinding type approach is often needed. For example, Taylor expansion based methods have been used to avoid instability (Mynard and Nithiarasu, 2008;Low et al, 2012;Coccarelli and Nithiarasu, 2015;Coccarelli et al, 2016). By applying such method, the semi descrete form of Eq.…”

“…Applying the fundamentals of finite element method, i.e., linear weighting and shape functions, (readers are referred to (Nithiarasu et al, 2016) for more details) to Eq. 7 gives the fully discrete form of the implicit Global Taylor-Galerkin (GTC) method as ( = 1),…”

Therapeutic heat and cold in cardiac rehabilitation

“…Three-dimensional models represent thermal changes in a human body close to reality but are, however, difficult to apply. Therefore, the segmented models that consider various biological and physical processes may be the preferred models [93]. Investigators have considered alternative models to describe whole-body heat transfer, from just two nodes describing core and periphery (for example, Gagge [94]) to multi-segmented, multi-layered models.…”