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.
