Precision in thermotherapy is obtained by providing a reverse gelling polymer composition which gels when its temperature is raised towards body temperature. The composition is injected into the blood supply of the tissue being treated, at the beginning of thermotherapy. The temperature increase caused by the heating rapidly gels the composition, which temporarily blocks the flow of blood in the region being treated. This improves the predictability and stability of treatment. On cessation of heating, the composition gradually dissolves, removing the temporary embolization. The use of local heating can also expedite removal of tumors and the like from soft organs, even when the heating itself has no therapeutic effect.
