Numerical modeling of temperature distributions within the neonatal head

Introduction of hypothermia therapy as a neuroprotection therapy after hypo xia-ischemia in newborn infants requires appraisal of cooling methods. In t his numerical study thermal simulations were performed to test the hypothes is that cooling of the surface of the cranium by the application of a cooli ng bonnet significantly reduces deep brain temperature and produces a tempe rature differential between the deep brain and the body core. A realistic t hree-dimensional (3-D) computer model of infant head anatomy was used, deri ved from magnetic resonance data from a newborn infant. Temperature distrib utions were calculated using the Pennes heatsink model. The cooling bonnet was at a constant temperature of 10 degrees C, When modeling head cooling o nly, a constant body core temperature of 37 degrees C was imposed. The comp uted result showed no significant cooling of the deep brain regions, only t he very superficial regions of the brain are cooled to temperatures of 33-3 4 degrees C. Poor efficacy of head cooling was still found after a consider able increase in the modeled thermal conductivities of the skin and skull, or after a decrease in perfusion. The results for the heatsink thermal mode l of the infant head were confirmed by comparison of results computed for a scaled down adult head, using both the heatsink description and a discrete vessel thermal model with both anatomy and vasculature obtained from MR da ta. The results indicate that significant reduction in brain temperature wi ll only be achieved if the infant's core temperature is lowered.