Next Generation Anatomical Human Models and Thermal Application of Their Detailed Vasculature

Introduction: The latest generation of the Virtual Population (ViP) [1] includes YOONSUN V3.1 [2], a female model with unprecedented detail in nerve and vasculature anatomy, illustrated in Fig. 1. The newly segmented fine vessels (<2 mm) allow us to study the impact of the vasculature on in silico temperature increase estimations. While the impact of microvasculature is typically handled through a homogeneous and distributed heat-sink term, the thermal impact of large vessels is typically simulated by imposing a Dirichlet boundary condition [3] (37°C). An intermediate approach assigns the small vessels with a high perfusion of 250 times the normal perfusion of muscle. We compared these three different simulation approaches for the detailed vasculature in the YOONSUN model. This provides insight into the influence of the vessel tree detail on thermal modelling and provides an estimation of an upper bound on the impact. Methods: ViP model YOONSUN was investigated in the abdominal MRI imaging position at 3T, which constitutes a high exposure scenario [3] with a thermal hotspot in the right forearm. The Pennes bioheat equation [4] has been applied with thermo-physical and -physiological parameters from the literature [5]. The exposure level was normalized to the first level controlled operating mode [6]. Thermoregulated perfusion values were not considered for this study.