Ultrasound data are collected from a thermal source and a mass of tissue before initiating therapy to measure two parameters of the bio-heat transfer equation (BHTE). The parameters are the thermal diffusivity (K) of the tissue and the magnitude of the thermal source (Q). Once the parameters have been obtained, the BHTE can be calibrated to the specific mass of tissue and the specific thermal source. The calibrated BHTE can be used to generate a temperature dependence curve calibrated to the thermal source and tissue, and spatio-temporal temperature maps, to facilitate pre-therapy planning. During therapy, ultrasound data are collected to determine if Q changes during therapy, and if so, the BHTE is recalibrated using the new Q value, increasing an accuracy of the temperature estimations.