Simulated temperature distribution of the proximal forearm.

Temperature changes in the resting proximal human forearm have been studied non-invasively, using computer simulation. A procedure for spatial model generation, based on digitized slice data, has been applied. A mathematical model and a 3-D computer simulation program have been implemented. Heat transfer in the non-homogenous tissue was modeled with a well known bio-heat equation. The heat production by tissue metabolism was modeled using the Q10 rule, while the heat exchange between the blood and tissue was modeled as a function of local temperature and regional blood flow. The stability and accuracy of the method was confirmed by varying the simulation parameters, the initial and boundary values, and the model dimensions, with subsequent analysis of the results. We have explained, by computer simulation, the variations in the Pennes' well-known in vivo measurements of the steady-state temperatures along the transverse axis of the proximal forearm. Suspecting that the anatomical positioning of his measuring probes varied, we have reconstructed their possible positions by searching for the simulated positions that result in the best agreement between simulated and measured temperature fields. Our simulations indicate that the fluctuations of the measured steady-state temperatures should not be smoothed out because they are the natural consequence of a complex interplay between the position of the measuring probes, anatomical position of the main arteries, dimensions of the forearm, blood flow, inhomogeneity of tissues, and environmental temperature.