Solution of the linear bio-heat transfer equation

Abstract
In Nyborg (1988 Phys. Med. Biol. 33 785) an expression was given for the temperature elevation at a distance r from a small source which has been generating heat at a constant rate for time t. It was stated, without proof, that the expression is a solution of the linear bio-heat transfer equation first proposed by Pennes. This article gives a brief derivation of that solution.