A therapeutic apparatus (300, 400, 500, 600) comprising: a therapeutic system (302, 402) for treating a target zone (304) of a subject (306), wherein the therapeutic system has an adjustable focus for directing radiation (410) into the target zone； a respiration sensor (308, 310, 416, 424) for measuring a respiratory phase of the subject； a processor (322) for controlling the therapeutic apparatus； and a memory (326, 328) containing machine executable instructions (340, 342, 344, 346, 348, 350, 352) for execution by the processor, wherein execution of the instructions causes the processor to: send (100, 206) control signals to the therapeutic system that cause treatment of the target zone, receive (102, 208) time-dependant-respiratory-phase-data (330) from the respiration sensor, generate (104, 210) focus-adjustment-control-signals in accordance with the time-dependant-respiratory-phase-data, and send (106, 212) the focus-adjustment-control-signals to the therapeutic system.
