The invention provides for a medical instrument (100) comprising: a high intensity focused ultrasound system (104) a magnetic resonance imaging system (102). Machine executable instructions (180, 182, 184, 186) cause a processor (144) controlling the medical instrument to: receive (300) sonication commands (160), wherein the sonication commands specify a set of multiple target volumes (202) within the target zone； and receive (302) a selection of a current target volume (200) selected from the set of multiple target volumes. The machine executable instructions further cause the processor to repeatedly: acquire (304) the thermal magnetic resonance data by controlling the magnetic resonance imaging system with the thermometry pulse sequence commands (164)； calculate (306) a temperature map (168) using the thermal magnetic resonance data； control (308) the high intensity focused ultrasound system to sonicate the current target volume by steering the sonication location to the current target volume； remove (310) the current target volume from the set of multiple target volumes after controlling the high intensity focused ultrasound system to sonicate the current target volume； calculate (312) a sonication energy (172) for each of the multiple target volumes by using the temperature map； select (314) a next target volume from the multiple target volumes using the calculation of the sonication energy for each of the multiple target volumes, wherein the selection of the next target volume comprises searching for the sonication energy with a minimum value； and set (316) the next target volume as the current target volume.
