Nodal Network Simulation of Transient Temperature Fields from Cooling Sources in Anesthetized Brain

Transient thermal gradients in the brains of anesthetized cats and rabbits due to localized cooling to 5°C with probes of two different shapes were modeled successfully to within 0.5°C by a computer program utilizing a finite difference method and thermal coefficients of water, without addition of a term for metabolic heat or blood flow. Input data to the program required temperature measurements in the brain away from the probe, although in the cylindrical case it was possible to use the probe temperature as the forcing function by assuming that the probe had a larger diameter than was actually the case. The results indicate that for the experimental conditions, metabolic heat and blood flow can be adequately accounted for by means of a rather small adjustment of the thermal diffusivity term in a general diffusion equation, without need of an explicit term for such distributed sources.