The invention relates a method and an apparatus of predicting or planning a temperature distribution (52) in a body. The method comprises the steps of: a) obtaining a model of the body (50) related to a temperature transport mechanism or temperature distribution (52) in the body; b) simulating an application of heat to at least a part of the body such as targeted tissue; c) determining and/or predicting the temperature (52) or heat distribution in at least a part of the body using the model of the body (50).