A medical apparatus (300, 400, 500, 600) comprising a magnetic resonance imaging system (302). The medical apparatus further comprises a heating system (320, 502, 601) operable for heating a target zone (321) and a processor (326). Execution of machine readable instructions causes the processor to receive (100, 200, 700, 800) a treatment plan (340). Execution of the instructions further cause the processor to repeatedly: control (102, 204, 704, 804, 900, 1002) the heating system, using the treatment plan, to heat the target zone during alternating heating periods and cooling periods； acquire (104, 208, 702, 706, 802, 806, 902, 906, 1000, 1004) magnetic resonance data using the magnetic resonance imaging system, and modify (110, 214, 712, 812, 1008) the treatment plan using the magnetic resonance data. The instructions cause the processor to acquire the magnetic resonance data during a cooling period selected from at least one of the cooling periods.
