One modality for destroying malignant tissue involves imbedding a small spherical heat source of radius ro within the tissue and maintaining local temperatures above a critical value Tc for an extended period. Tissue that is well removed from the source may be assumed to remain at normal body temperature (Tb = 37°C). Obtain a general expression for the radial temperature distribution in the tissue under steady-state conditions for which heat is dissipated at a rate q. If ro = 0.5 mm, what heat rate must be supplied to maintain a tissue tem- perature of T > Tc = 42°C in the domain 0.5 r 5 mm? The tissue thermal conductivity is approxi- mately 0.5 W/m · K. Assume negligible perfusion.