Estimation of the postmortem interval by the method of finite element modeling of postmortem heat transfer in human head

Abstract

Aim to develop a two-dimensional finite element model (FEM) of postmortem heat transfer in head to determine the postmortem interval (PMI). Material and methods. The finite element modeling of the geometry and postmortem heat transfer in an adult's head was carried out using the ELCUT 6.5 Student application. A hemisphere with a radius of 98 mm was used as a geometric model of the cerebral part of the head, consisting of evenly distributed homogeneous layers: the scalp, the bones, the cerebrospinal fluid of the subarachnoid space and the brain. For FEM validation we used the evaluation of the cooling curves convergence obtained by FEM and by the Marshall Hoare and Newton Richman cooling laws under conditions of constant and linearly varying ambient temperature. Results. A scalable two-dimensional FEM for finding the postmortem temperature field of the head was developed. The model allows for accounting any changes in the ambient temperature, combined heat exchange conditions and the dependence of thermophysical parameters of biological tissues on the ambient temperature. The FEM check-out under standard cooling conditions showed the maximum convergence of the results of finding the postmortem temperature field with the results of valid phenomenological mathematical models when only convective heat exchange with a heat transfer coefficient equal to 6 W/(м2К) was set on the outer edge. The developed FEM is characterized by the stability of the results of determining the prescription of death coming to deviations of the initial temperature field of the calculated region from its physiological level. Conclusion. It is advisable to use the proposed FEM in the forensic medical expert practice when determining the prescription of death coming.