1. Therapeutic system ( 1 ) comprising: a MR imaging unit arranged to acquire MR signals from a body ( 10 ) of a patient positioned in an examination volume, a thermal treatment unit ( 19 , 20 ) for the deposition of thermal energy within tissue of the body ( 10 ), wherein the system is arranged to perform the steps of: a) initiating thermal treatment by heating the tissue of the body ( 10 ) at the position of a focus within the examination volume, b) selective acquisition of MR signals from a first image plane ( 24 ), the position of the focus of the thermal treatment being located within the first image plane ( 24 ), c) reconstruction of a thermographic MR image from the MR signals acquired from the first image plane ( 24 ), d) computing a baseline thermographic MR image from the temperature distribution within at least one second image plane ( 25 , 26 , 27 ) being different from the first image plane ( 24 ), e) moving the focus of the thermal treatment to a new position within the examination volume, f) changing the position and/or orientation of the first image plane ( 24 ) corresponding to the new position of the focus of the thermal treatment, g) repeating steps b) and c), wherein the baseline thermographic MR image computed in step d) is used for thermographic image reconstruction in subsequent step c).